If my feet get cold, it's game over. I had someone tell me about boot blankets back in the late 80's but didn't get a pair till mid 90's. All I can say is they work wonderful for me and are well worth the little bit of weight they add to my haul. If it's really cold, I drop a couple of hand warmers in there and I'm good for an all day sit. I usually just wear a pair of uninsulated hulking boots and slip on the BB's as soon as I get set up. If you sit till your feet get cold and then put them on they do little good.