I've found that walnut by itself, without any additive, leave the cases clean, but not real bright. And the corn, leaves them bright and shiney.(at least when it's new) So, I usually run about a 50/50 mix, and will put in a tablespoon of Flitz media additive once in awhile. I have about a 3 hr. time limit on running the tumbler. Anymore than that, and if the brass is still dirty, I'll either add alittle additive, or change the media, if it looks dirty and wore out. I have talked with some reloaders at the gun shows, that will run there tumbler for 2 or 3 days. Way to long. Here's alittle tip also, run your tumbler on a basement floor if you can, or at least in a cool spot in a garage if you can. There is a fan in the bottom, pulls air up to cool off the motor. Put it outside in the sun, and you can burn out the motor faster. I've got a Lyman 1200 that's going well over 25 years old, and it still runs good. And there were times I was cleaning brass to sell, and might run 3-4 days a week, with only time to change the brass and media, when it got shut off. gypsyman