Yea I know till it gets clean. I was watching a video on the tube and they ran their tumbler for twenty minutes. They put some Blue Magic polish in there to help it along. I polish mine for two or three hours to get it clean. I am using Lyman corn cob media with a little Nu Finish car wax. I still have a little stain on some of the brass but that is OK just so it's clean. The Lyman seems to last for ever. I have cleaned over 2000 rounds of 45 brass this week and it's still going strong. The last media I threw out was so old I was ashamed to use it.
So how long do you let your tumbler run? Don