It's completely up to you whether to re-plan or not.
Since you have a TP (I assume), then you already have the bones of a good plan. So an extra hour could mean you can add in things you'd left out, re-riding favourites, taking it a bit slower. This is where Evaluate comes into it's own.
Or it could mean re-planning! Remember to make sure you force the optimiser to use your fastpasses. And take a copy of your current plan before you start, so you can revert if you want to.
Some people like a lot of replanting, others don't. Good luck