I on;y have my experience to go on here but I met my exh at 16, together 2 years, he cheated on me, we split.
A few years later we met up again, he was engaged to someone but we still had strong feeling for each other and he ended things with her and we got together (I told him I wouldn't do anything while he was with someone else) bu he still left her for me.
We got married a few years later, had a child, were expecting another and I discovered he'd cheated on me on a night out. I wasn't in any place to end things and desperately loved him and our family, he was so sorry, blah blah.
10 years later, I discover he he having a full blown affair at work. This time when he gets home his bags are packed and we are divorcing early next year.
He is still with the (12 years younger) ow 18 months later and I don't envy her one bit. He also can't giver her children as he had the snip after we decided our family was complete.
I guess my point is, he has cheated numerous times, not just with me so I have little to no reason to believe he won't do it again and I certainly wouldn't trust him knowing all this (which of course she won't...as far as sh'es concerned she is special because he chose her over his wife and kids, which eh didn't as I found out and kicked him out).