I'm not sure there's a parallel between cleaning chips and cleaning ashtrays, but here's what I do....

I clean ashtrays, glasses, china, and other items that won't be harmed by cleaning.

I don't clean postcards, playing cards, bars of soap, or other items that will be harmed by cleaning.

If I have a current chip that's dirty, and cleaning will do more good than harm, I clean it.

If I have an obsolete chip that's dirty, and cleaning will do more harm than good, I don't clean it.