Trouble is plenty of young people get into what they call 'stable relationships' at a far too early age.By the time they're 40 they've had enough of it,haven't lived, haven't travelled much, only nailed about 2 or 3 partners,kids are draining all their money etc etc.In my view there's a lot to be said for having a good look at the market until you're about 30 or so and then trying the old long term relationship thing.It what we did,worked for us. Up until then I must have nailed about 110/120 women, can't even remember all of their names now, as for the Mrs, I've never asked and don't really need to know.
Perhaps settling down early at 18/21 was relevant when the average life span was about 45/50 but when you're likely to live until 75/80 it's less relevant.