This has got to be a personal preference as everyone has a different tolerance of cold weather. I suspect my answer would be different if you were asking about and I had knowledge regarding remote mountain/wilderness hunting where weight and minimalist concerns are greater.
I hunt Illinois temperatures and conditions. Never too far away from the truck (i.e. less than one mile). I don't get carried away with any type of material, brand, or system. The only thing I do religiously is wear the minimum amount of clothing to keep me warm while walking to the stand and climbing the tree. I carry all of my outer clothing in a backpack and put in on in the tree as I cool down. The last thing I want to do is sweat. I buy thermals in the spring when I find them on clearance and wear them until worn out. For extreme cold, I have a bib and parka from Cabelas. Extremely warm and waterproof.
My undergarments including socks get washed in scent proof detergent after each use. Outerwear gets washed before season and rarely thereafter unless I feel they are compromised.