The door seals form an airtight seal in the freezer. Mildew can form on the door seals, which can cause an unpleasant odor and can cause the seals to become brittle and crack. If the seals are not in good condition, they may be unable to may a proper seal to the freezer cabinet. This will result in cold air loss, poor freezer operation and increased compressor cycling.
Periodically clean the door seals with a toothbrush and a solution of warm water and baking soda or water and bleach. Gently pull the seal to expose the folds. Be careful not to pull too hard or you might tear the seal.