I guess my question would be what would happen if he does have an affair. Is that a deal-breaker for you or if he is having a MLC and does something stupid and realizes it was the wrong thing, would you work through that with him. Sorry, I know that is a crappy thing to think about.
When H and I seperated after a year of marriage he had an affair and I went home to live with my mom. After a year and a half of being apart we got back together and we've been married 7 more years. Guess they weren't the best years b/c/ here we are now but I am glad I forgave him and we stayed together. If he does it this time around I think I would file.
Your H thinks he can get away with anything so can he? If not maybe knowing that if he does it, it will be over, maybe that will keep him from maing that mistake.

M:29 H:30
Married: 8 years (together 10)
6/14/07- Seperated

For God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.
2 Timothy 1:7