The down is still very usable as long as the bags still have close to their original loft. I have a mating pair of the Trailwise Slimline bags, bought in the late '70s, that are still as good as ever. They used the best down available at the time, but not the 800 fill power you see today. Probably more like 600, which is still good, it just means that the finished item will be a bit heavier. The Slimlines weigh 48.7 and 47.9 ounces and have about 6.75" and 6" of loft, respectively (short length, up to 5'8"). I've occasionally thought about re-purposing the down (or selling them, but they're like old friends...old friends that need to be washed.)
If you sew, there are lots of possibilities...vest, quilt, bag, or all of the above with that much down (probably 3lbs or so). A baffled sleeping bag is a big project, though, and recycled down may be poor economy.
I don't know if Feathered Friends in Seattle would consider making you something using your down, but it can't hurt to call.
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