If you don't mind it, I would see no reason to worry. Will you be okay on the occasions when the therapist does not run over? I find the problem to be that people get used to it and get hurt or feel punished and so forth when the therapist is capricious about such things. If you won't be, then I see no reason to worry about it.

I keep the time and leave exactly on time. I usually walk in a minute or two late. For me, I do not like being at the mercy of the therapist so I don't let the therapist make those decisions.