I am sure that the majority of guys record their sessions. After all, they want to get their money's worth. And saving some for later ensures that they can give themselves a "freebie" every now and then.
I try to keep my eyes on their hands. I also try to make sure I give them plenty to do with their hands. Sure, they may have already set up the recorder beforehand, but if they haven't, I do my best to try to prevent it.