My T is nearly always on time, and we nearly always end on time...and she manages it well. I think it's all in how the T wraps up sessions. My T always starts wrapping things up about 5 minutes before the end of the session. If I'm mid-conversation, she'll let the session run a bit long, but we rarely go over time.

There have been a few times where my T has been running late - usually because she was dealing with an emergency. She will always let the front desk know that she's running late, and she always makes up the time with me.