Anybody can choose to clean a chip at anytime they want. They can do it today, tomorrow, next year, or ten years from now. Once the chip has been chemically tampered with (unless it is in very high grade condition to begin with) one usually can not restore the worn chip to its original color and/or condition ... and the harsher it has been cleaned the more un-natural it looks. Personally speaking, other than for esthetic considerations ... I can see no valid reason to clean a worn chip. If one is concerned about germs ... lightly spray a mild disinfectant on the chip.