Every trip!!
I think when we plan out our trips in our heads, we think of the days as endless possibilities - we will wake at sunrise and go to sleep well after midnight and still feel rested even though we just walked 15 miles during the day (and are used to a sedintary lifestyle).... and with endless trips, and with Disney pixie dust, we want to do sooooo much and get to do everything we think would make our trip magical. Then, reality steps in. We get tired, so we sleep a little later. The time we thought we would go over to Winter Summerland to finally play mini-golf got eaten up in a rain storm. We think it would be great to go see that hotel you hear so much about but you the bus to Downtown Disney took 40 mins to get there....and at the next stop had to load a scooter. Before you know it.....our trip is winding down and we are on the trail of tears lugging our suitcase behind us - promising next time we will be able to see this and do that. (And we start to plan our next trip! Damn you Disney! Damn you!)
I know for me, I dream about Dole Whips at least once a month. I talk about them to everyone. I can taste it. I can smell it. And then I get there and run right to Aloha Isle my first day and swear it will be the first of many. But then I have a late breakfast, or I don't want to spoil lunch, or I may be over at Space Mountain and do I really want to walk over there when I have a fast pass for Pooh in 15 mins....and it also ends up being my only Dole Whip of the trip.
It just gives me reasons to come back again, and again, and again... oh, how I wish I had a trip planned!