Simo and Cicci recommend

You can store the spanakopita in an airtight container in the fridge for up to 3 days. Just reheat it in the oven to enjoy.

If you want to prepare the spanakopita in advance, assemble it without baking, cover it with plastic wrap, and refrigerate overnight. Remove the wrap and bake the pie according to the recipe instructions.

You can also freeze spanakopita either raw or cooked: in the first case, prepare the spinach pie normally but do not bake it. Wrap it in plastic wrap and freeze for up to 2 months. Remove it from the freezer, remove the wrap, and bake at 350°F. There’s no need to thaw, but it will take at least ten more minutes to cook.

If you want to freeze it after baking, let it cool completely and wrap the pieces individually to freeze them. Remove a piece from the freezer and reheat in an oven at 350°F for about 20 minutes, no need to thaw.