I don't know about once a cheater always a cheat as I think at the end of the day is down to your beliefs! Do you think you'll trust him again? Would you be likely to bring it back when you argue? If he has been able to do it once, what stops him to do it again?
Even I, I can't answer those questions for myself, and I'm trying to save my mariage with someone who has cheated on me for 2 years!
I believe with time you'll be as to decide if once a cheat always a cheat, and if he shows true commitment to save your mariage then you might be able to answer your questions
