It is generally recommended to store muffins in an airtight container at room temperature for up to 2-3 days. If you plan on keeping them for longer, it is best to store them in the fridge or freezer. However, keep in mind that storing muffins in the fridge may cause them to dry out, so it's important to store them properly in an airtight container. If you do store them in the fridge, allow them to come to room temperature before serving to enhance their texture and flavor.