We find if we stay less than five days we don't have enough time to do everything we want to do. More than six days and we start getting really annoyed with the crowds, kamikaze stroller attacks, loud teenagers, waits for the bus, etc. If we stay five or six days the entire trip seems to be magical. We also have started planning the Magic Kingdom days early in the visit while we are still refreshed. Animal Kingdom and Disney Studios are better for later in the trip, as the crowds there are less likely to get on our nerves. It's sort of like visits from relatives. We love every minute of it - up to a point!