Spare liners for felt pack boots are far from unheard of here. even if you are a young one - which I guess I'm not anymore

Unless I've got a stove (i.e. a hot tent) in winter, I usually have an extra set if I'm gonna be out multiple days. Heck, I just found a new-to-me third set at the local army surplus store as one of mine has been getting pretty ratty.