Storing instructions: store in an airtight container in the fridge for up to 4 days, or in the freezer for up to 2 months. To thaw, transfer to the fridge overnight. Once you are ready to use the frosting again, remove it from the fridge and let it warm up to room temperature. Then, using an electric mixer or a stand mixer, whip the frosting back up until it is nice and fluffy.