I bought a 5 pack of Hot Hands insole foot warmers for my Canadian deer hunt. These were rated for 9 hrs. and they did that and more. They allow me to wear a lighter boot and stay comfortable all day. I've since bought a 10 pack and used up half of those.
My S-I-L turned me on to sunflower seeds while on a fishing trip in early fall. I've now taken them to the deer blind where in greatly helps pass the time. It has helped kept me in the blind longer each day. Be careful of the sodium as each brand varies. If your trying to quit chew, this would be a winner.
Those hand warmer and foot Warmers are great. I've used them for years. In Canada and anywhere less I'm sitting in extreme cold I found that those boot blankets work great. I buy them too small to wear over my boot, but remove my hunting boot once on the stand- change socks to a dry pair then throw a few hand Warmers in the boot blanket and zip them up.