We've been lucky enough to plan for every 4 or 5 years. When we went in '00, we decided we'd try for a cruise in '05 - so I put it on my Outlook Calendar at work and had it remind me one year in advance. However, when the 7 for 4 came out a couple years ago, there was no way we could pass it up! That was to be our longest disney stay EVER!
We "cheated" and tried Universal and Sea World last summer. After we got home, my reminder for my '05 cruise popped up. And while we still cannot afford a cruise, we will manage to get in a trip this May. But if we go back to our original 4 to 5 year schedule, this will most likely be our last trip with DS14. But oh, the fun we'll have when we're empty-nesters visiting by ourselves...
Well, maybe I'll try to talk DH into just one more trip with DS.