Store cupcakes, frosted or unfrosted, in an airtight container for up to 5 days. You can also bake the cupcakes in advance and freeze them until ready to frost and serve. Once the baked cupcakes are cooled completely, place them on a baking sheet in the freezer until firm, about an hour, then transfer to a freezer bag and freeze for up to 3 months.  When you're ready to frost the cupcakes, pull them out of the freezer and either let them defrost first or frost them while frozen. Let the cupcakes defrost for about 1.5 hours before serving.