Buttercream can last up to 2 weeks in the fridge if made with milk or butter, but it is at it's freshest if used in one week. However, once on the cake, it will only last about a week in the fridge. ... However, if not made with milk or butter, your buttercream can last for up to 6 weeks before going bad.

Does buttercream frosting spoil?

When stored properly, buttercream frosting can last in the fridge for up to a month, and in the freezer for up to three months. ... Why would you want to make buttercream ahead of time?

How long can buttercream last unrefrigerated?

​How Long Can Buttercream Sit Out at Room Temperature? A buttercream made with a recipe consisting of butter and shortening can generally sit out at room temperature for up to 2 days. We suggest covering your treat with plastic wrap or placing it in a cake carrier to prevent your buttercream from crusting too much.