My mother and father used wool-filled sleeping bags while they were still camping and backpacking; this was in the 40's and 50's. I kept one of the wool bags for a while after my dad retired. It was like a rolled mattress when rigged for carrying and had lost most of its original loft over 20 years of use; it was more like a thick blanket after some use. Also, it was heavy and not particularly warm, even when new.