Haha. This is a good question. I would say it depends on individual. Some guys cant stop looking at pretty girls although they have GFs. But that doesn't mean they'd jump into the bed with the girls they stare at.

But for some who are very loyal to their GFs/wives, then they won't do that eh? Like the saying, 'Love is blind'. So no matter how plain their partners are, they only see them in their eyes. Sappy, yeah. But some guys do admit like that to me when talking about their GFs. Lol.