I remember when we left the after our first visit that my parents "absolutely" never wanted to go back. The last time they had been there only the Magic Kingdom existed and during that trip...Epcot and MGM had come into play and they were just exhausted. (Of course, the last time they went they only had one child and this time they had 3)
The funny thing was, a couple weeks after we got home, they decided that they wanted to go again. So, we wound up going back 8 months later, and then again a couple months later. They now go the same week every year and never complain about it.