[B]Is case tumbling really necessary?
I've reloaded for years, and when my cases get too dirty, I just wipe[/them off with a Flitz cloth and go back to loading.
Seems to me as if this is one of those "Range Myths" (as opposed to Urban Myths) that are fueled by the industry to sell products that aren't really necessary].
About the only result of all this time and money is cosmetic; if that appeals to you, go for it. I'll continue on my scruffy way.