Depends on several things...
in Dawn's case, if she baked it earlier in the day, it would have been room temp and wouldn't have taken very long to reheat. If it's baked the day before and refrigerated, it will take a lot longer of course. Also, the size pan, etc. But for a cold large pan, I reheat for about an hour covered at 350 (making sure the top is well-sauced with some reserved sauce if it looks dried out), then uncover, top with some more cheese, and finish off for about another 15 minutes uncovered. But then, my pan is big.