I do try to control time and the ending. I try my best to call time on time and leave straight away. I notice my T sometimes has trouble with that because the last quarter of the session if most often when we are finally able to get into the meaningful work, and T seems to be reluctant for us to leave in a triggered or switched state.
Sometimes I am not present enough to call time. In that case T brings the session to a close, either close to time or a little over time is she is able to.
I try my best to do it myself because I find it really triggering to be told time is up. Strangely I never even thought to set a timer or alarm on my phone.