The “2 year itch” in a relationship?

Yep, defo been there and I would reckon most men and women have, even if they don't rationalise it out, though IMHO anyway it's more likely the woman who will go or stay when it comes up. Back in the day when I helped moderate the personal issues forum around here the 2-3 year itch thing was quite evident when relationship stuff would come up. It was definitely a pattern. To the degree that it was sped up or slowed down depending on how often a couple would see each other. So living together would tend to speed it up, only seeing each other at the weekends would tend to slow it down.

I seem to recall reading that there may be some science behind it too. IE that humans have something like a reproductive cycle which in general terms has about a three year length. Long enough for the first child to be weaned onto solid food as the hypothesis goes. Pre contraception that first year where everything is new and you're at each other like rabbits you'd end up with a pregnancy. That in love stage would carry all the way through that and the birth and early babyhood and the love for the baby would offset any drop in passions for each other too and further kids if you stayed together would solidify the relationship into that long term familial phase.

Today along with all the other stressors and expectations and choices in our lives that's more skewed. So outside of accidents few new young couples are going to have a pregnancy and child in the first two years together. Children themselves come much later into the picture for most in the West and we have fewer of them. So I suppose more couples are in a situation where the focus is entirely on each other and when that initial honeymoon period has passed we're more likely to take stock and ask questions.