When the freezer is full of frost, this process is impeded and the freezer has to work harder to maintain a consistent temperature. This not only raises your energy bill, but it can also shorten the lifespan of your freezer. In addition, frost can make it difficult to open and close the freezer door, and it can also obscure your view of what's inside, making it more difficult to find what you're looking for. For these reasons, it's important to defrost your freezer on a regular basis.