I did cakes for DDs 1 and 2's birthdays a few weeks ago. I made the cakes on Wednesday, did the buttercream on Thursday and refrigerated them. Did the fondant covering and decorations of one set on Friday for the party Saturday. Covered the second set with fondant on Saturday for a party on Sunday. They were all fine, very fresh and lasted another couple of days. I threw one lot out on the Tuesday and the other I'd put in the freezer on the Sunday night after the second party.