I always tumble, and then wash, my semi-auto cases. This is because they flop around on the ground, and when I pick up mine, I always pick up some of somebody else’s, which may have been sitting around for a while.
But how about revolver cases? You fire them, eject them back into a container, and take them home. They don’t have a chance to get dirty, or sit around and corrode a bit.
Generally I always tumble pistol brass between loadings. However, for my revolver cases, especially big bore cartridges I will load them a few times before I tumble again. They aren’t shiny but they don’t really get dirty either.
I’ve quit reloading for a while, but when I did, I always tumbled revolver brass. The finished round just looks better, and I like working with clean stuff. It probably doesn’t matter, just makes me feel better.
I always tumble brass because the finished product looks better and the dies stay cleaner. For me, reloading is about producing a higher quality product than the factory ammunition that’s available. I do run a progressive, but I don’t look to cut corners to save time. Of course if you’re not anal retentive like me, then do what works for you.