Shelf-Stable Frostings

• Most cupcakes can be stored at room temperature, as long as the frosting you decorated them with doesn't contain highly perishable ingredients. Types you can leave at room temperature include cupcakes frosted with buttercream frosting -- made from shortening or butter, ganache, chocolate buttercream and royal icing. Some of these frostings do contain dairy products or egg whites, but the sugar will preserve them for two to three days. Royal icing is often made with powdered egg whites and dries to a hard finish -- reducing the risk of foodborne illness. Canned buttercream frosting generally contains shortening, as well as preservatives, making it safe to leave at room temperature.

No Refrigeration Needed Ever

• You can refrigerate cupcakes frosted with buttercream, royal icing or ganache frosting if you wish, but there are a few types of frosting that should never be refrigerated. Boiled seven-minute frosting resembles layers of warm marshmallow fluff, but the frosting becomes hard and gummy if you refrigerate it. Fondant, while used infrequently on cupcakes, should never be refrigerated or frozen.

Extra Frosting

• In all cases, cupcakes stored at room temperature should be eaten within three days. After that, both the cake and the frosting may begin to spoil. Storing leftover frosting is another story, and each type of frosting has different requirements. Store buttercream frosting in a covered container in the refrigerator and use it within two weeks. Store royal icing covered at room temperature for up to two weeks. Chocolate ganache frosting can be stored in the refrigerator for two to three weeks. Gently reheat it to spread it or use it to make truffles.

Chill Out

• Although the most common frostings don't need to be refrigerated, a few must always be kept chilled to reduce the risk of illness. Whipped cream frosting is made from whipped cream stabilized with gelatin. It has a light, creamy texture, but is firm enough to pipe. Even when refrigerated, whipped cream frosting breaks down within about two days. Cream cheese frosting holds up well, but should be refrigerated because it contains perishable dairy products. Swiss, Italian and French buttercream frostings are made with butter that's been whipped with lightly cooked eggs. These frostings are lighter, richer and creamier than regular buttercream frosting. Cupcakes frosted with them really should be eaten right away, but refrigerate any leftovers. Place frosted cupcakes in a covered plastic container and store them at 40 degrees Fahrenheit or cooler. Use them within two to three days.