One person can't manipulate the same person for the rest of their life. Eventually they will stop believing anything the person says. The point of manipulation is, however, to get what you want when you want it. It's not meant to be a lasting thing with manipulating the same person over and over unless the person is stupid.
I'm not saying you're dumb, and you don't seem like the type to be manipulated long term. However, you might fall for one or two tricks and that could be all the guy needed. Know what I mean?