They’ll last for 3 days if kept in an airtight container at room temp, 5 to 6 days if kept in the fridge, or up to a couple of months in the freezer. If you opt to go the freezing route, wrap each muffin carefully, preferably in something airtight like a zip-top bag with all the air sucked out to prevent freezer burn. To serve after freezing, let defrost for about 20 minutes at room temp, then warm using a toaster oven or a quick zap in the microwave.