I've found that 5 day parkhoppers work best for us. In our case, that means early travel, get in the parks around noon the first day. Then 3 full days. Then on the last day, leave around 3 and take a later flight home. We do enjoy the ability to hop to CA when DCA gets full; and we also enjoy the leisure to get out of the parks when it's hot and crowded midday, and go back to the hotel for a rest. With 5 day parkhoppers, you have plenty of time to see and do what you want, without rushing it or withstanding the busiest part of the day.