Homemade Pastéis de Nata can be stored in an airtight container at room temperature for up to 3 days. If you’d like to keep them longer, consider refrigerating them, where they will last for about a week. However, it's important to note that refrigeration may affect the texture of the pastry, so for optimal results, enjoying them fresh out of the oven is highly recommended. If you need to reheat your tarts, the best method is to use an oven. Preheat the oven to around 180 degrees Celsius (350 degrees Fahrenheit), and warm the tarts for about 10 minutes, or until they are heated through and regain some crispness. Avoid using a microwave, as it can make the pastry soggy and lose its delightful texture.