My T starts the sessions exactly on time and ends exactly on time. I don't watch the clock because I don't want to be responsible on time. It is on my T to end the session on time. I am lying on the couch so I will not see the T's face but I will still notice when he starts to throw glances at the clock and so I know that the session is about to end soon. I guess my internal clock is also quite well tuned already and I would start feeling weird after the 45 minutes have passed without actually having to look at the clock.