I have never heard about quilts in the freezer to run the freezer more efficiently. But I have always been told a full freezer will use less power than an empty one so I add milk jugs of water to keep the freezer full. When I need the space in the freezer I remove the jugs but do not empty them just let them set in the heated garage until I need the water to water flowers and vegetables. I try to conserve wherever I can.