I was with my xh for 18 years in total, married for 11.. We were very different people but before the dcs came along it wasn't so obvious.
He became very successful in his career, travelled abroad 50% of the time.. over the years, he was unfaithful and gave me an STI, stopped having sex with me, became more and more grumpy and tired when at home (probably jetlag apart from anything else) - took little interest in the kids and none in me.
It wasn't one big thing (despite the infidelity - we got through that!!), but lots of little ones, like not being able to share interests cos all he would talk about was sport and business. I was just his housekeeper, and a single mum half the time anyway. I felt that I was selling myself, cos we were well-off but I was more and more unhappy.
I just felt totally lonely, and knew if I stayed with him I would become more and more bitter. We split when I was 39 and although it's been a bit of a roller-coaster I am so much happier today.
He has turned out to be a much better xdh than dh; he sees the kids regularly and supports us and now I'm not tied to him I can respect him for what he does do instead of hating him for what he doesn't.
I still don't know why he never wanted to have sex with me though..