I'm all for saving money. I have been called frugal and been called down-right-cheap and I can't deny it but to spend all that time trying to clean worn out media when the price of new media is so low, even I wouldn't do it...
I'm not too cheap to clean my media. FF to 3:00. Jerry Miculek isn't too cheap, either. Maybe he doesn't know about Drillspot. Or lizard pet bedding. Or maybe he has found out that cleaning media is actually very efficient use of your time.
https://www.youtube.com/watch?v=O5y_dsP3dsM
It is ridiculously fast to clean media. I just put all my media (about a tumbler and a half's worth of corn cob) in a large plastic bag with a few cups of clean water, mash it around a bit, then I twist up the top and squeeze. The water runs out black. Then dump it into a tray and leave in the sun to dry. I only do this maybe a couple times a year. I'll buy more media when I finally run down to only a tumbler full.
It does wear out when the sharp edges wear off round.
I have not found this to be the case, at least with corn cob. It doesn't matter how rounded the media is, the way I use it. The mineral spirits removes the carbon deposits. And the polish shines up the brass.
That said, I don't tumble my brass to make it shiny. I tumble only long enough to dry the brass after washing it in hot, soapy water. That's about 45 min to an hour, typically. It depends on the season and how big and wet the load of brass it. By the time the media and brass is dry to touch, the cases are smooth, clean, and even-looking, but not actually bright yellow like new brass - unless I left the tumbler running while out and about for a few hours. They're basically clean and shiny, but a very slight, even layer of tarnish that formed while they were washed/tumbled will still remain. If I want to load them right away, I will follow that by putting them in the oven for an hour to make sure the primer pockets are dried, thoroughly. Or I leave them in an open top container for a few days before packing them up.
For a time, I just washed and dried in the oven, but that leaves a lot of streaking and uneven, dark tarnish if you don't wash them real thoroughly; I don't wash them real thoroughly. Really tarnished brass looks kinda neat, though. I have a couple of batches of brass for revolvers and bolt actions that hasn't been tumbled in years. They look a little like steel case Russian ammo from a distance.