Paint, nothing. These are far easier for the money and time (http://www.4keyboard.com/).
...זה גם יכול להפוך הקלדה בשפות אחרות קל יותר
...if that's your thing.
Most dome switch keyboards can theoretically last until the PCB traces begin to oxidize or the rubber rots. If you keep it clean and dry, it'll probably be fine for years. 95% of keyboards are dome switch, especially cheap ones.
That said, I hate typing on dome switch keyboards. Buckle springs forever!