First I threw my Rocky Thinsulate boots in the garbage. I've been told that Gortex is much better, I don't know, never had that much money to spend. I have issues with Rocky boots saying they are waterproof, they are water resistant at best, and I nearly lost some toes because of it. Any boot that requires the owner to spray with silicone is not WATERPROOF! Not that Rocky is the only Chinese made boot that advertised falsely, but they are the ones that froze my toes.
With that said, it's like many have said, dry feet are happy feet. Socks are the key. Thin layer of a great wicking sock first. I like Cabelas Ingenious socks, thin, medium and heavy, a sock or combination that's good for all weather. Just like boots and shoes, buy the socks a size bigger too. Especially the outer sock if you wear more than 1 pair. Too tight of socks is as bad as too tight of boots.
I replaced my Rockies with Muck Woody Elite boots. Still made in China, but an all rubber, 100% waterproof and breathable. I've hunted from 70 degrees to lower teens so far and with the right socks they've always been warm and dry inside. Never thought a rubber/neoprene boot could do that, I've been very happy with them so far. I don't expect they'll work for much colder, but my friend has those over the boot bootie things and he swears by them. That might just be the ticket. Otherwise it's my old Sorels, good to 100 below and about 5 lbs each. lol
American by birth, hunter by choice.