8 hours?
That's an extremely long time, what media and cleaning chemical recipe are you using?
Are you trying to get them to perfect like new condition, just spendable or what?
Cleaning up wrecked coins like old nickels is one thing, took me awhile to get some rusted steel cents and really crusty tokens back to decent shape but normal clad not near that long.
Just a short time will knock off enough dirt to get past the dirt sensors in Coinstar machines, but you could even use a handheld shaker bottle with a little aquarium gravel and dish soap to accomplish that.
To get them good enough to look decent and not be embarrassed when cashing them in at most banks I rarely have to tumble more than a couple of hours.
Just natural aquarium gravel, water and a drop of Dawn dishsoap.....i actually decided not to run them again, and yea, just want them to be spendable.....the V and Shield I just threw them in because it couldnt make them any worse, but also didnt really help much either...the V has no date and the Shield I can only read 18.....thanks for the advise Digger, I havnt tumbled before so I didnt know how long to run them for lol