12 nights. We decided it was 2 nights too long. The next year we did 10 nights. Seemed about right, so we did 10 the following year. That seemed a day or two too long. The next year we did 9 nights. It seemed perfect. The next year we split Universal/Disney, and did 3 Universal days and 7 Disney days (9 total nights). That worked out really well for us, and that's become our standard length of stay now.