I stayed, for about 18 years from when I first found out he was a player ( kids were 1 and 4 then) until my son left school.
I thought the kids would be better off with two parents than one, and especially because my ex was in the armed forces. If I'd left, the kids wouldn't have seen much of him at all . I'd have had to go back to where my family was to get any support, and my parents would have been very negative about it, since they had very conservative attitudes about separation and divorce.
So I stayed, and we lived more-or-less like brother and sister for those years. It wasn't horrible at all, he was a good father if not a good husband, and he kept his private life separate from family life . The kids had a good life , although they now say that they had a pretty good idea that Dad was unfaithful because of little things they saw or heard.
I left him when both kids were grown up ( 19 and 23) and it was a big surprise to everyone including my ex , who'd thought that we'd just keep chugging along as before and had no idea that I'd been planning to go for years.
My kids now say that they would have been fine if I'd left sooner, but that is just them talking, because they didn't have to experience it ,and so they have rose-coloured glasses on . In reality it would have been a lot harder than they imagine !
Ex and I got a divorce and we're both remarried now. My DH is like a father to my kids and grandchildren, but my ex has ghosted my kids and me in favour of his "new family" . That is painful for me to see - I don't care if I never see him again but it's awful that he doesn't see his kids or grandchildren ( probably through bitterness about the divorce I guess ).
I don't regret the way I handled things at all. Living with him was like living with my brother - it may not be the way other women would want to live, but I made a decision based on what I thought was best for my kids at the time.