Most Helpful Guy
Cheating is about sex, pride and control. A man who feels respected by his wife and gets his satisfaction is very, very unlikely to ever cheat. On the other hand, if the woman controls everything, makes him feel like a dog (by nagging all day long about anything he's doing) and puts her own pride before his satisfaction, then she shouldn't wonder, if he gets elsewhere what he covets.
As a professional marriage counselor, I get to see and to hear a lot... But you can pretty much breakt it down into that simplification I wrote above.
A content man will most likely not cheat, even if the woman grew past the blossom of her youth...
On the other hand for women it's mostly the case, that she doesn't feel coveted by her man anymore. Then she goes out and gets one who gives her the feeling of being worth being chased.