Our visits tend to be around 10 nights, this gives us all the time to see the parks at a leisurely pace, revisiting the ones we like ans a day for a water park and one day for resort relaxing, shopping and dining. Any less is rushing and any more, we done it all and will wait for another trip.
We don't do a park first day unless we have AP's and after a couple of days of parks, we never stay with one park in a day, we hop, its wind down, overload time and a waterpark excursion. Couple more days of parks and a DTD shopping spree, resort pool and wandering and then more parks and we're ready to come home. We can only eat resturant food for so long and loaf and by the time the 11 day rolls around, we thanks Disney for the fun and memories and are ready to come home.