If you have large session rooms, you need more than 10 minutes between sessions for people. If you have only 10 minutes per session, you need to be sure that speakers end on time. If you let speakers run late, you have to let people in before he or she finishes. Otherwise, you get a mob:
When you know a room is going to be absolutely filled, why do people always sit in the aisle seat of an empty row, requiring everyone to climb over them? You’re only committing to staying an hour, folks. Go ahead and risk sitting in the middle!