My DH and I had WDW passes from our trip in May 2000. We bought a 7-day pass and ended up hanging out at the Dolphin hotel pool for 2 days. As a result, we each had 2 days left on our passes unused. When we went to DL in October 2001, we brought them along and were able to use them.
The only thing is that you have to go to the booths where they sell the tickets and let them know that you have WDW passes. They made us wait because the kids in the booths didn't know what the procedures were. However, their manager came to help us and to compensate for us having to wait, he gave us automatic entry to go on any ride we wished without have to line up. What a wonderful gesture!
I don't know if they have changed the policies since we did this in October 2001. But it worked for us, because our WDW passes indicated (the fine print on the back) that they were applicable at any Disney park, not to mention that when we bought these passes at the Dolphin hotel, they made a point of giving us that information.
