In another thread I mentioned that I recently bought a pair of BMW Allround boots. A member sent me a PM asking how to treat them. The little booklet says, basically, "brush off dirt, clean with a damp spong." Think I could have figured that out. The question mark is "treat regularly but moderately with leather care (suitable for Gore-Tex.)"
My best guess is that you want to treat the leather parts with something which lets the leather "breathe" so the Gore-Tex can do its thing. Any of you have Gore-Tex lined boots with better instructions? There are certainly many other brands of boots with similar construction. Clearly we don't want to use any of the many waterproofing treatments, right?
Another tip I just remembered, and did to my new boots: soak a very small piece of clothe with one of those vinyl protectants made mostly for car dashes and run it over both sides of your zipper. Then run the zipper up and down several times. You will be amazed how much easier the zipper works. These plastic zippers are everywhere. You may be moved to give the same treatment to many other zippers.