Through 1968-1970 I was stationed in Alaska and part of your cold weather issue was the white Mickey Mouse boot (black are Korean war issue) the air valve you are seeing was to help with decompression of the boot at high altitude when flying. I had a horrible time with them do to my feet sweating and then the interior of the boot would ice up, I finally turned to the Air Force canvas and felt pac Mukluk's which allowed moisture to wick out. Cablea's cold weather boots are designed much the same way (iditarod). There are many boots and options capable of keeping your feet warm. Today I use a Rocky Sno-stalker boot that seems to work well, I also use artic shield boot covers when I wear lighter boots and they will keep me warm from dawn to dusk in November.