If you are just giving your T notice, I would just do that. It's a professional service like Brian says. However, if you're interested in terminating, which is a process for both parties, I'd tell him the beginning of the next session you wish to terminate and see what develops. It could end the end of that session or he may suggest X numbers of other sessions or whatever but there'd be a real, joint discussion.

My termination took eight or nine months.