I want to make my fondant cupcake toppers ahead of time. What is the best way to store them so they don't get hard? Any suggestions are appreciated.

Freeze them maybe? I don't know. I would dry them out (which means that, yes, they will harden) or just make them fresh.

lay them over parchment or wax paper and then slide them into a zip lock back and lay flat in the freezer. When you need them, take them out and use them (they'll be as soft and fresh as the day you made them). If you have a lot of decorations, lay them over layers of parchment or wax paper inside a plastic container that seals shut and freeze. When you take them out of the freezer, remove the layers right away and lay them apart so that if they start to condensate, they don't stick to one another. I do this all the time and it works like a charm.