It's partly a matter of what you become accustomed to.
As a youngster growing up in northern Manitoba, Canada, and then later on in central Alberta, being outdoors for extended times in temperatures well below freezing for extended periods of time was commonplace. I played ice hockey through my youth, and for a good portion of those early years it was on outdoor ice rinks. Organized "league" games were usually cancelled when the temp got to below -10 F (about -23 C).
A great deal of my hunting is still done in below freezing temperatures. The same with trapping and ice fishing. Now into my 7th decade, my circulation is definitely not what it once was, and I am inclined to abide by my own rule of thumb ... "If it's not fun, I'm not going", and it's never fun if I'm soaking wet, or freezing cold. The technology involved in producing clothing and gear to keep us warm and dry has certainly come a long way over the years though, and those little hand warmer things are a must have in my pack these days. Of course sitting relatively still in a blind or stand makes it far more difficult to keep warm than if you are moving about.
Just a note for those who care (or don't), that we've been burdened locally ( central British Columbia) with a fairly snowy, and relatively cold spell the past few weeks ... overnight temps have been in the -20C to -30C range. Throw in a bit of a wind chill, and there's a real need to bundle up when heading outdoors. Seems to be trending up a bit now ... close to noon, and around -13 or -14C.
When not shooting, I enjoy ice climbing and Ski touring. Scottish winter climbing is a cold affair which can involve sitting or standing on a belay for an hour at a time. Two pairs of socks has been the most successful formula I have found.
A liner sock; merino wool bridgedales. Then merino wool ski socks over the top. These are long socks that go to the knee and can be rolled up or down to help regulate temp.
Any more than that and it becomes difficult to get blood into the feet.
Yeti gators are often added by people for colder times/ higher altitudes. Berghuas do some. They go over the boots and insulate from the outside.
Previous suggestions of pads to sit on are spot on too.
Buffalo sallopettes are what I wear when
It’s really cold, over a pair of man tights but with the same two pairs of socks. They are fleece lined, pertex outer clothing and supremely warm. Can zip the sides to vent too.
Bridgedale Summits Socks are the ones I was talking about in my earlier post. They do two types. One ankle length - good for those who wear leather boots (hiking or army type boots) and knee length which are great for wearing with wellies. I got mine at TK Maxx.