Serial monogamy is the key here I think!!!
Too much importance is placed on marriage, so what if people are living together, "living in sin"
pile of bollox. We are married, was a decision we made and we are happy with it, just celebrated our 8th anniversary this week. But if we were commited to staying together we would have been together this amount of time whether married or not.
We had a civil wedding, but I cannot understand people who are atheists, agnostics, or even two sets of pagan friends (!!!!!) who have had church weddings!
But back to the serial monogamy thing, I reckon that would be fine. I will hazard a guess here, but I always tend to get these things wrong... different species of animals have differing numbers of partners, and as a general guideline, the longer the dependance of the young, the more likely the parents are monogamous. Looking to my brothers and sisters, human young are dependant on their parents over the age of 25
(I left home at 19, married at 20, the rest of my siblings all still live at home
) Anyway, based on that, I would say long term monogamy suits people overall. But, if two people are not working together as a couple, why should they stay together? I would definately say that effort to keep a relationship going should be put in, but why flog a dead horse?