I have an Oliver No 9 typewriter which I recently acquired and some of the keys are a bit faded, although its fully functional.

Although I'm not ready yet to launch a restoration project, I'd like to use it and am in a bit of a conundrum as to what to do maintenance wise.  I assume using the typewriter will fade the keys more, although I have no idea how fast that happens (surely not that fast, as its about 100 years old).
Is there some kind of clear lacquer you can put on old typewriter keys to help keep them from fading, and then of course if you do so, I assume you would make it harder to ever touch the lettering up again, if that is even possible.
Thoughts???