Over the past 35 years we have been waiting longer and playing the field more before settling down. According to the Office for National Statistics, men are getting married for the first time seven years later and women six years later. This means that the average man is aged 32 when he asks “Will you marry me?” and the average woman is 29 when she says “Yes”.

But is this trend towards the thirtysomething marriage making us happier and more satisfied? And when it comes to the fortysomething crunch - the most common age for divorce - who is most vulnerable: those who took the plunge early at twentysomething or the ones who waited until thirtysomething?

When couples seek my help as a marital therapist, I start by asking for the history of their relationship. People who married in their twenties often report tough times at the beginning: living with in-laws, financial problems or moving around the country as one partner climbed the career ladder. Most couples overcome these problems, but sometimes there are unfortunate knock-on effects; for example, from hurried and unsatisfactory love-making because they felt inhibited about being overheard. Also, couples who marry relatively early can grow apart, especially when one partner has been successful at work, travelled, met new people and grown in confidence while the other has been home-based.

Is the grass greener elsewhere?

However, the greatest threat to the twentysomething marriage is reaching 40 and wondering if the grass could be greener elsewhere. This is particularly dangerous when someone who married his or her first love starts fantasising about what he or she has missed. The temptation to have an affair can be overwhelming and very damaging. By contrast, the thirtysomething marriage seems to sidestep these problems. At this age people are more established in careers and can start a relationship on a firm financial footing. They have a clearer idea of who they are and what they need from a relationship. When these couples reach their forties, they are less likely to be nostalgic or curious about the single life.

Yet, when faced with fortysomething couples in crisis, I always feel more optimistic about the outcome for those who married in their twenties than those who married in their thirties. Why should this be? If you marry later, you are more likely to bring old baggage into your relationship. In some cases, I help couples to unravel the influence of someone from maybe two or three relationships back. For example, to someone who once had a suspicious partner - forever quizzing them about their movements - an innocent inquiry such as: “What time will you be back?” can sound aggressive.

A more insidious problem of marrying later is higher expectations. This is because one of the best ways of recovering from a failed relationship and starting to look again is to tell yourself: “I deserve better”, or “Next time I'll meet Mr or Miss Right”. There is nothing wrong with this strategy. But unfortunately, if the next relationship does not deliver, the bitterness becomes that bit greater and the desire for perfection that bit stronger. On many occasions, the body language of these clients seems to be saying: “I've not survived all that single crap to be treated like this.” Worse still, these resentments tend to be unspoken and unexpressed, and become hardened into a barrier.

The final issue about getting married at thirtysomething, particularly your late thirties, is the need to start a family almost immediately. Many couples have no time to get to know each other properly or put down solid roots together. If a relationship has been built on long weekend lie-ins and brunches, the demands of small children can be a shock. This sense of isolation is worse if the grandparents are correspondingly older, too, and not fit enough to help.

By contrast, the couple who married at twentysomething have a longer shared history of both good times and bad times. So when faced with a crisis in their forties, they can look back and feel a sense of pride about past problems overcome. Their body language is often more dogged, suggesting: “We're not going to let this defeat us.”

Having started their relationship with lower expectations, they are markedly more tolerant of each other's failings and more prepared to compromise. Most important of all, they have watched the other change and have knocked the rough edges off each other. Meanwhile, the couple who married in their thirties, when they felt fully formed, are less flexible and more likely to have a “take it or leave it” approach to their partner.

It's the commitment that counts

What about people who met in their twenties or thirties but did not get married until much later, or have still not tied the knot? What counts, ultimately, is making a deep and abiding commitment; this could be a joint mortgage, starting a business or having children. However, getting married does change a relationship, even if a couple have been living together for years. It creates a formal bond between two families and sends a strong message to friends, employers and the world that this is an important and valued relationship.

Although the ultimate deciding factor for the success of a relationship is the character, determination and generosity of each partner (and that is not determined by age), my advice is always to seize the day and commit. There is nothing sadder than hearing a client talk about a past partner who, with benefit of hindsight, was ideal but who he or she let slip away because “we were too young”. I used to think they were talking about a relationship from their teens, but time after time my clients were referring to their mid-twenties and regret not settling down while they could.

Although we want to believe that we will go on for ever, life has a natural rhythm and cycle. Economic and social pressures might be pushing us towards not settling until later, but the truth is that it is always easier to follow the seasons.

Andrew G. Marshall is a marital therapist and the author of I Love You But I'm Not in Love With You (Bloomsbury Publishing, £8.99)

FOR: LUCY MCDONALD

“We'd have married even earlier if we'd met in time”

I got married when I was 26 and my husband 28. It was a whirlwind romance and although my friends and family said they were delighted, they were also clearly shocked at the speed of events. There were even bets at the office where we both worked as to whether we'd last until Christmas.

That was eight years ago and - at the risk of sounding super-smug - I am pleased to report that not only are we still together but we are still happy.

Although marriage is usually part of a predictable progression within a relationship, for us to do something so ordinary seemed out-of-the-ordinary, partly because none of our friends had plans to settle down but mostly because neither had we until we met each other.

We saw marriage as the beginning of a great adventure. The first five years were spent having fun. We went backpacking, lost entire weeks in bed and in each other and, both being journalists, drank copious amounts of expense-account wine when we should have been having lunch with contacts.

We now have two beautiful daughters and a massive mortgage, and although I would be lying if I said we feel like lovestruck teenagers every day, when times get tough we draw strength not only from each other but also from the knowledge that our family is built on foundations forged entirely from love, not convenience, body-clock-related desperation or unromantic inevitability.

Our first year of marriage was probably the hardest as we learnt to adjust to the rhythm not only of each other but of married life. For example, he liked staying in bed. I rose with the lark. I liked long walks. He preferred short taxi rides. His ideal Sunday was in the pub watching football. Mine in Ikea's soft furnishing department. I liked rock music. He liked Leonard Cohen.

We are still very distinct people but we have learnt to compromise and appreciate our differences. These days I am a connoisseur of the all-day lie-in, while he loves walking. I still hate football but realise that hell is Ikea. We saw Leonard Cohen last month and both agreed it was the best concert ever.

Neither of us can really remember what life was like before we met, and without wanting to sound too tragic or irritating, I think we'd have married even earlier had we met in time.

AGAINST: LIAM PLOWMAN

“We were both still working on our identities”

I married in both my twenties and my thirties. I was 28 the first time and my wife was a fresh-faced 22. While we're talking numbers, it's probably worth mentioning that our combined emotional age was about 17. We were both carrying baggage, not from previous relationships but from childhood and adolescence, which meant that we were both still working on our identities. We weren't unusual in this respect; 21st-century Westerners enjoy a protracted adolescence, during which it can be risky to make any “commitments”.

Anyway, we had been together for two years before we blundered into marriage. Our reasons were laudable enough - love, wanting to be together, that kind of thing. What we hadn't done was to talk seriously about what we wanted from life, in terms of kids, careers, where to live, what values to hold dear and so on, probably because we didn't have a clue. About three years into the marriage it became apparent that our views on these matters were diverging. The relationship began to unravel and I was divorced by the age of 33.

After a three-year courtship I remarried last month, at 37. When Claire and I met we both had well established careers, friends, values, wants and tastes. Far from making us inflexible, part of the fun has been exploring each other's substantial worlds. I met Claire's host of interesting friends; she met both of mine. I showed Claire how to eat oysters; she taught me that some flowers are edible. I was introduced to the wonders of Cornwall; Claire quietly doubted my sexuality as I shared my love of musicals. We both had disposable income and our own flats, so our courtship was characterised by great meals out, holidays, lazy Sunday mornings...it was sophisticated, hedonistic and fun.

Not in a way that left us unprepared for toil and practicality, though. We had our first child a year ago and our life is unrecognisable from that described above, but we love it - and each other - even more, because we were ready and we knew what we wanted. So, for me, unless you are a particularly precocious or self-aware twentysomething, the thirties are a better bet for marriage.

LIAM PLOWMAN

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