Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. Reheat individual portions in the microwave or bake in the oven until warmed through. You can also freeze the casserole for up to 2 months; just be sure to cover it tightly with plastic wrap and foil before placing it in the freezer. When you're ready to enjoy, thaw in the refrigerator overnight and bake as directed above, adding a few minutes to the cooking time if necessary.