The T'day tickets are the most important to book early. You really can wait on the winter break ones as the kid's schedules are much more flexible.
The school is open on 11/21 although some profs will cancel classes. We have always taken the chance and booked for Tuesday night. So far, so good. You might want to wait until you see a class syllabus for the Wed classes.
The final exam schedule is posted, but some classes will not have finals or assign papers that can be turned in ahead of time. We have never had trouble booking winter break tickets at reasonable prices much closer to December when S's finals schedule became clearer.
http://www6.miami.edu/UMH/CDA/UMH_Ma...2326-2,00.html