Leather boots will eventually soak through, it happens, ive hunted the backcounrty with feet of snow on the ground and my leather boots eventually broke down and soaked up the water. I used Sno Seal everyday to try and fight this, but a good rubber is going to be your best bet for full waterproof, try Schnees boots. So finding a cure doesnt not seem to be in the future, a constant water will eventually find its way in on a porus material like leather.