I'm not an expert or anything, but here is what I've observed and what my guesses are.
Most people apply 10-15 schools. I might be a little high, but not too much. Just about everyone (except for a Rhode Scholar I know) has applied to 8+. A few exceptions get above 20, and are typically California people. Personally, I've sent my AMCAS to 14 schools but only sent secondaries to 13 (left out Tulane)
Most people interview until they get in where they want to go. I'm guessing people are scheduling every interview invitation they recieve until at least October 15. After they recieve an acceptance they are happy with, then people will probably withdraw applications or turn down invites. This next part may be wrong, but it is just a hunch. I think a lot of top schools seem to be interviewing later on in the season (Harvard, Penn, Northwestern, etc.), while a lot of other schools seem to be interviewing people with really high stats really early (state schools, lower ranked schools). Personally, I have 7 interviews scheduled. My life would be a lot easier if I knew where I was in or out to determine where to interview or not.
So far, I haven't found it really hard to manage class and interviews, althought that might change at the end of the semester when professors typically cram material in and it will be the heart of the interview season.
Just my $.02. Good luck with it all.