Hi Rich,
I just returned from a Walt Disney World vacation, so I have first hand knowledge of this issue. On our very first day, the Seven Dwarfs Mine Train closed shortly before we were supposed to ride. We were all sent emails to let us know there had been a change. We were given a FastPass+ selection that could be used from the time our original FastPass+ began until the park closed.
This information also showed up on
My Disney Experience. We were given a variety of attractions to choose from, including the Seven Dwarfs Mine Train. Our choices ranged from Space Mountain to Peter Pan's Flight. We were fortunate that the Mine Train started running again so we were able to enjoy that attraction.
The same thing happened when we visited Animal Kingdom. Kali River Rapids was not operating during our original FastPass+ time so some of our group used that selection for Expedition Everest instead. Each time the replacement FastPass+ selection was only valid until park closing. We were not offered a return time for the next day.
Thanks for visiting us at the Disney Parks Moms Panel. Be sure to let us know if we can help you with any other questions!
Wishing you a magical day,
Amy H