I think that any of my ts would fill my usual time slot if I were to not come in for a while. In fact, if I am going to miss a session for some reason, they do see someone else at my usual time. If I wanted to be sure that a particular time/day was available after a break, I would go ahead and schedule appointments for when I wanted to come back. All of my ts have a waiting list, so I don't think it would be fair for me to expect them to keep my time open. How would they know if I decided to just not come back, even though at the time I thought it would just be a break.
If I did take a break without an end date, I would expect to have to wait a couple of weeks from whenever I called to get back in to see him/her. And it would probably take a few weeks for them to have a regular opening (same time, same day) for me.