Quoted from phishrace:A tumbler is kinda overkill for balls. Just polish them regularly using a cotton rag and metal polish. I use Blue Magic, which I bought at a nearby auto parts store. You'll get the same results in much less time. 5 minutes a ball tops. When the rag stops showing black (dirt), you're done.
Regularly polished, decent balls will last (stay shiny as hell) for 10 years or more in home use. Buying new balls every year or when they get dirty is probably the biggest waste in this hobby. Besides making them look like new, most polishes leave a thin protective coating on the ball. No reason not to polish them occasionally.
It does depend on the game too though. My RFM tears up pinballs quicker than my other games. I think the ball hitting the metal bracket does this
