If you aren't using gaiters already you might want to try it for some added warmth. I use some cheap neoprene ones with an uninsulated boot with wool socks/liners and it's good down to the mid 20's for sitting a couple hours easy, walking it's good all day. I think the boot blanket idea is good idea for on stand also. I don't own any but have a friend that had trouble with cold feet so I gave him a set of Arctic Sheild boot blankets, no more problem for him, he loves them.
