A: A good down sleeping bag can be one of the longer-lasting pieces in one’s gear quiver. They’re not (usually) exposed to wind, abrasion, and rain, the nylon or polyester shells are really quite durable, and the down filling typically holds up much longer than its synthetic cousin. My brother uses a Feathered Friends down sleeping bag that I purchased some 18 years ago, and it’s still going strong (albeit it never saw extended heavy use). Another issue is that one can become cold in all sorts of odd situations, due to fatigue, lack of food, damp underwear, whatever. So because you were cold that one night doesn’t necessarily mean the sleeping bag has croaked.

That said, the bag may be near the end of its natural life, or in need of some TLC. If you really like the bag, it’s certainly worth trying to save it by taking it to a laundromat and washing it with a down-specific cleaner such as Nikwax Down Wash ($9; www.rei.com). Dry it thoroughly in a dryer, tossing in a few tennis balls to knock the down clumps around and break them up. Then give the bag a good shake and lay it out. If it was rated to minus 20 when new, it should have at least six inches of loft. You also should be able to hold it up to a bright window or light without seeing voids in the down.

If the bag is flattish and voids appear, then the bag is kaput. That’s the way it goes—25 years is a good, long life for any piece of outdoor gear. New bags rated to minus 20 aren’t cheap, but if you think of it as a long-term investment, they’re not so bad. Western Mountaineering’s Puma Super Microfiber is a minus-15 bag that has lots of durable 850-fill down and a high-performance polyester shell. It’s $510 for a regular-size bag (www.westernmountaineering.com). EMS also still makes bags, of course, including the Mountain Light -20, which uses 725-fill down and costs a bargain $299 (www.ems.com). It weighs four pounds, versus the three pounds, four ounces for the Puma, but that’s not too bad.

For a comprehensive selection of sleeping bags, visit Outside Online’s Sleeping Bags Buying Guide.