If I asked for extra time, I would expect to pay for it. If the therapist went over time without me asking for it, that would be on his tab.

It was sort of a non-issue in my case, because my out-of-pocket copay was the same no matter what the length of the session, but it allowed him to bill insurance for his services if we did go overtime in some way, and occasionally that certainly happened. (Would be one benefit to therapists who do accept insurance.)