First, he isn't the sneaky one, she is. This happened to me a couple of years back when my wife was going to school and then working a couple of hours in a lab before coming home. She use to bring one of her gfs over to visit and then she would head out. One of her friends told me that it was her understanding that they were to make me happy and that included having sex since she was so busy with her school schedule. I told her I didn't believe that, so I asked my wife when she got home that night and she said I should have some fun since her schedule made her such a drag. So I took her at her word, and I fucked several of her friends over the next 3 years. My wife got her degree, got a great job, and I'm back to being a one pony show. But it sure was fun while it lasted.