i figured out my problem but i don't understand what it means. at some point i switched to white legends on black keyboards. these are the ones that always fade and eventually rub off. back when i used white/grey boards with pad printed brownish legends they would last for years.
Chances are your old boards, unlike the newer ones, actually didn't have pad printed but rather lasered or dye sublimation lettering.
The options for lettering black 'boards in a durable way are somewhat more limited, that's true. Basically what you can do is:
* plain pad printing (will be gone rather quickly)
* pad printing with transparent wear-proof plastic coating over legend ("decals", e.g. Logitech Classic 200) or whole key (e.g. Filco)
* lasered lettering using either a plastic that becomes lighter (dye destroyed by heat) or lighter-colored plastic in-fill, e.g. current Cherry G80
* two-shot / doubleshot molding (most expensive and most durable, e.g. old black Focus, NeXT, older dark Cherry POS boards)
Maybe go through the various Wiki articles on the subject if you haven't yet.