Keep the frosted cake in an airtight cake container in the refrigerator for up to 5 days. You can freeze the unfrosted cake layer for up to 3 months when wrapped tightly with plastic wrap and foil. Thaw frozen layers overnight in the refrigerator before decorating. Warm individual slices at 300°F for 8 to 10 minutes if you prefer a softer texture. Add a small spoonful of fresh frosting after reheating for a creamy finish. Discard the cake if the frosting smells sour or the surface develops unusual moisture.