Once you've prepared your Oreo Mud Pie, any leftovers should be stored properly to maintain its freshness. Cover the pie dish with plastic wrap or aluminum foil to prevent freezer burn and keep it in the freezer. Properly stored, the Oreo Mud Pie can last for up to 1 to 2 weeks. However, for the best taste and texture, it's recommended to consume it within 4-5 days.