Sorry to be the sole discontent on this subject
But I really cannot imagine doing this. Two parks, possibly, but three or even four, to me just sounds like a colossal waste of time. I cannot even think about the amount of time it would take just getting from one park to another, plus getting into the park, getting to the rides you want to go on, etc. When we go, some of the parks hours are 9:00 - 6:00, of course with World Showcase being open later.
Good luck to those of you that would chose to do this. Maybe the difference is that we go every other year and always know that we will be back to see everything again. I suppose if this is a first trip or a once-in-a-lifetime trip, you would want to cram everything in. But the best advice I ever read in a Disney travel book, is really to plan well, and then take your time while in the parks. How many families do we all see right around 3:00, where the kids are either crying or yelling, and a parent is obviously irritated and just want to get to the next attraction. No one is having fun in that scenario. So we take time to notice little things and get an ice cream cone whenever we want, or just sit on a bench and people watch. I know my kids, and they would not have a good time, if we were to go from one park to another to another and maybe yet to another all in one day.
Again, this is just my personal opinion
