to both clockitnow and whoa nussie!:
first, congrats - pretty sweet to have choices. since i know both of you have been accepted at tri I, i want to clarify something - something that needs to be clarified each year, i suppose:
Any schools that want to hear by April 15th need to back off
this is not uniformly true. if a school starts part of their program by a certain date (mandatory summer rotations, for example) - then april 15th is their date. you can check the aamc rules on this if you want verification.
however, if you have revisits that take place after that date, and you are seriously interested in those schools, then programs like triI will most likely give you extensions [they do verify that there is a revisit you will be attending]. also understand that you can hold as many waitlists as you want past both the april15th and may15th dates, you just can't hold multiple acceptances.
since i went through this same dilemma a few years ago, i do have some advice. first - i did matric at triI, and i did so after their deadline only because i was revisiting 2 schools. i ended up going to ~6 or so revisits. this was silly. i was admittedly a little confused about where to go, and the revisits were very helpful, but there were definately some that i knew-with reasonable certainty-i would not be attending unless something amazing happened.
the number of revists you want to attend is up to you - but i can assure you that the novelty will wear off, and there will be something about each school you visit that you like. i would say that 3 revisits sounds reasonable - but this number is somewhat arbitrary. remember - it is not only your time - but a schools money, and an anxious waitlisters spot that you are holding.