Whatever your preference is. I prefer to have my chips just the way they are. If they are dirty, I leave them that way and, if they are clean, I will not make any special effort to dirty them up. I collect used good condition chips - to me, it shows that the chip had table experience, a life of its own, a history behind it (who knows who may have touched/used the chip?). Where as most people collect only mint/uncirculated condition chips. To me, what's special about a chip that someone got right out of the cashier's cage and put it in a drawer or jewelry box for years? Bottom line, what makes you happy?!

Thomas