You want to make sure it can breathe, so do not encase it in plastic. Instead, store it folded or hanging in a closet, covered with a cloth bag. It should be in an area where it is not compressed and has room to stay fluff. When it's time to bring it back into service for the colder months, take it out of its protective bag and give it a good shake to redistribute the filling, and you'll be good to go!