Here's the problem with deadlines: you give him a deadline of October 1st, and he'll just take that as permission to continue his affair until September 30th, at which point he'll promise you the moon and the stars to take him back.
It's like giving the terrorists the date that you're going to pull out all your troops -- same concept.
I like INTERNAL deadlines, for YOU, but all you should tell a wayward spouse is that "my patience is not limitless," and keep it vague.
