Nope. After making changes to the registry I restarted the multicast service, and rebooted. Then ran a small patch task to the machine and could see the downloaded patches hit the SDMCache folder. I've tried running inventory scans as well in case that could possibly trip it off.
We even tested upping the deletion time back up to 4 days, running the task to update SDMCache and then setting the clock ahead 4 days and seeing what would happen. No dice there either.
At this point, I've reset the reg back to the default 2 days, rebooted again, and rerun the patch task to the machine to update SDMCache with new files. I was going to just check on it Monday, and if they're still there start looking for other possible causes.
Is there a minimum amount of time that you can set those registry settings too? We'll eventually have it set to 14 days, but for testing I was setting it down to a matter of minutes.