Usualy that is the ramp up period. Your first few days should be pretty light. Toward the 21-22, it will start to add up. I would suggest really hitting the parks hard the first few days, then take some down time, and use the end of the vacation to see things again, and to explore DTD, the resorts, etc. I also would highly recommend going to Epcot on one of your last days and see all the storytellers and decorations. The parks and resorts are usually pretty well put together, but Epcot takes it to a new level IMHO.