In November the Seven Dwarfs Mine Train went out as soon as we returned for our FP time.
They told us to come back.
We did. Had a bit of a wait when it opened but not as long as those in the regular line.
And would add that I have had FPs for later at night and had the ride go down (specifically Space Mtn). I brought the FPs back with me the next morning on the off-chance they would honor them. And they did. All I did was ask nicely and almost before I could finish the question they said "yes".