There never really was a discussion of how long a session actually takes, as far as I remember. But after seeing my T for over 4 years, usually the sessions go for about 50 minutes, when I have little to talk about sometimes it's only 40 and if there's a lot of things coming up we usually go over, the longest session was about 70 minutes. It's a bit different every time, usually we end after about 50 minutes, give or take a few.