What Rob says is true, from a certain point of view (a little SW reference there). There is no FP+ from the official start time forward (e.g. 7:00 p.m. for the Halloween and Christmas parties). Be aware that, for the parties, you can enter as early as 4:00 p.m. Between 4:00 and 7:00 p.m. FP+ is still in effect for "regular" attractions.