The best way to preserve the flan is to refrigerate it because there is no risk of its texture changing, although, unfortunately, this method only keeps it for a few days. You can store the flan in the freezer, but I advise you to leave it in the fridge before, at least a few hours, so that it settles better and does not break when frozen. The store-bought creme caramel, either the powder or already prepared, can last a long time if sealed. However, its shelf life is reduced once open, especially the flan that comes ready in a sealed container.