I know there are two thoughts on this, and to each his/her own, but I say keep the polished brass look up. I remember once, while visiting the West Point Military Museum, setting my eyes upon a Colt manufactured Gatlin Gun. The thing was a work of art, and all of it's brass hardware was kept clean and gleaming. I guess it's easy to just let brass tarnish, no effort needed on one's part. But, to maintain the beauty of the brass as it left the manufacturer... well, takes true effort and care. Yup, if it's simply a tool to a person, and absolutely nothing more, then leaving it to tarnish is just fine. But, if the item is more than a tool to you, if it represents craftsmanship, history, sentiment, or something else, then why not take the care to keep her as she was made... Showing it is worth your time to do so. Just my opinion, and that's all it is.