When we went we got the Castle Package and we're done in under an hour....after getting photographs done we basically were done and walking back into the park with the beginning of the rope drop crowd (we had 8:00 appointments).
However, I'd say the amount of time you set aside for it kind of depends on the time of day. With the first appointment of the day, I would definitely say an hour is enough time. However, the later it gets in the day, the greater chance you will possibly have to wait a bit longer for your appointment (if they are running behind). If you have a later appointment of probably plan on 90 or so minutes, just to be on the safe side.