"Two can live as stupidly as one," observed the poet Philip Larkin, caustically noting the preponderance of some couples towards irritating self-satisfaction.
Even more annoyingly, it seems that happily marrieds really do have something to be smug about after all. A study of the benefits of relationships has confirmed a truth that many on the socially conservative right have long held to be self evident: marriage is good for you.
Not only does it boost physical health in men and mental well-being in women, but the longer it endures, the greater the benefits all round, resulting in a longer and more satisfying life.
Writing in BMJ Student as part of the journal's forthcoming Valentine edition, Dr John Gallacher and David Gallacher of Cardiff University's School of Medicine were asked to ponder the question of whether relationships are good for health. They argue that for a long time the functionality of nuptials was based more on legend than on empirical evidence.
"Traditionally, people thought it was a good idea and nearly everyone was married, so it was hard to make a comparison. But over the last 30 years there has been a lot more social diversity so we are able to make these evaluations. The bottom line is that medically speaking, the group with the greatest longevity are the marrieds," said Dr Gallacher, himself happily hitched for 30 years.
The paper cites a study involving millions of people over many years across seven European countries, showing that married couples had mortality rates 10-15 per cent below the population as a whole. This figure rises with the longevity of a marriage.
The selection hypothesis argues that well-adjusted individuals are more likely to establish long-term relationships, suggesting that the determining factor might not be marriage itself, but more the kind of people who are likely to wed and stay wed.
The authors argue that commitment is also linked to higher living standards, with the associated network of supportive families, shared friends and healthy lifestyles bringing other substantial benefits - not least that single men are likely to drink alcohol to excess more than their married counterparts.
Yet research also shows that not all relationships are good for you. Age is a primary determining factor, it is claimed. Adolescents in exclusive romantic relationships are more likely to suffer depressive symptoms, while the optimum age for a man to commit is after 25. For a woman it is 19-25.
This may be because 25 is the age at which most men become established in their careers and find themselves financially self-supporting for the first time. The age for women is likely to be related to their reproductive needs, it was claimed.
The authors argue that the existing evidence suggests that cohabiting relationships tend to be less enduring, while having lived together before marriage statistically hastens the sad road to break-up and its resultant health problems.
And while children can offer "long-term satisfaction", in the short term they bring considerable demands on parents' emotional maturity.
Meanwhile, women who find themselves in "multiple partnership transitions" are likely to have poorer mental health and increased mortality, it was claimed.
The paper also argues that while civil partnerships should theoretically confer the same benefits as heterosexual partnerships, by offering the same support networks there is still insufficient evidence to support any long term theories.