To boost the longevity of down-filled products, wash them as infrequently as possible — ideally in a bathtub (the gentle cycle in your washing machine will also do) with warm water and a low-sudsing detergent, such as Nikwax Down Wash (go to www.nikwax.com for stores), says Wade Woodfill, product director of equipment for sporting-goods maker the North Face, in San Leandro, California.

Afterward, gently press the water out, toss the item in a dryer set on a low temperature setting, and add a couple of clean tennis balls to declump the down. Never dry-clean down — the harsh chemicals strip it of natural oils, causing breakage.

When storing, fold the items loosely and keep them in a breathable fabric or paper (not plastic) bag. It’s also important to avoid compressing or putting heavy objects on down-filled items for extended periods. “The pressure will stress the filling and break apart the down clusters,” says Chris Bradley, president of Cuddledown, a bedding maker in Portland, Maine. “Over time this will reduce the loft, which causes down to lose warmth.”