Yes, you can store it at room temperature for 1 - 2 days, in the chiller for up to 2 weeks, or freeze it for up to 3 months. Immediately after whipping it up, transfer to a well-sealed, airtight container. Thaw frozen buttercream overnight in the chiller. Before using, re-whip the buttercream in a stand mixer fitted with a paddle until it's light and fluffy again.