Sport Aviation had an article buy a guy who maintains a Spartan Executive. Gorgeous airplane, you can barely look at it as it shines so. He said that polishing is never done, you're always polishing. What really got my attention was when he began discussing the crap that accumulates around the rivets. Dirt, old polish, bug gut and other assorted stuff. 4,000 hours just for the rivets.
Most of the polished aircraft I've seen are poorly maintained. To me polish is in for a penny, in for a pound. If it isn't really really shiny it isn't worth it.