Try Mean Green and an ultrasonic for cleaning first before tumbling.

I just change mine every game

A game or 2. Some are dirtier than other thoughs for sure though.
What cleaner/stuff are you using in the tumbler?

I've heard dryer sheets can extend the media life by removing some of the dirt.
Has anyone done this?

No because I can't imagine being that cheap.
Plus, all my dryer sheets are in in paper towel rolls in my dorm.

I usually use about 20% Mean Green. The tumbler isn’t great at cleaning, I find stuff gets covered in walnut dust if it is grimy.
If something is really cruddy a prespray of Mean Green and a dose of Magic Eraser might help.

Medium to dark brown is about right. You definitely want to clean things before you tumble them. I might get close to ten tumble sessions with the same media.

If you ever see the media turning grey, you may also notice the parts are clean but not shiny. You'll want to dump it all out and start again.

I don't smell what you did there.

I usually pull a cup or two of old out and a cup of new in when I do a session. The old stuff will give a better polish, but you need the new stuff to cut down to it.

Got that trick from when we polished tokens at D&B. I don't think they do that as much anymore.