If you can afford it, I would suggest that you add all of the schools that you are thinking about/planning on applying to now. The earlier they get a file going for you, the better it is now. The ~30 dollar fee per school is nothing in the grand scheme of things if it helps you get into where you would like to go. Don't go crazy and apply to 30+ schools, but make sure that you have a good number of schools listed and you can screen them later by secondary and interview if necessary.