I have been told some products with silicone will STRETCH the leather in your boots, and doesn't let them breathe. I just use simple bees wax type products. My feet are healthy, don't smell much, so i guess i'm doing something right. They manage to stay dry, even in one of the wettest parts of the continent where I winter. I put my boots in front of the wood stove for an hour before gooping them, and always take out the laces (and replace them) to get in all the hard to get spots. Getting in the stitching is important. I find wool socks are good in these kind of boots. Cotton socks SUCK! I carry lots of clean socks, and let my feet and boots breathe several times a day. My feet generally feel good to go when I look after them. I have had palantir fasciitis (painful foot condition in the tissues on the bottom of the feet), from carrying packs that are to damn heavy, and not having full shank heavy boot. A good few pairs of proper boots, and less crap in my pack when I travel have fixed that.