Unless I'm mistaken, you and I are talking about the same thing, Mike. The mail message have an expiration date, but the user is using some mail rules to set the date for specific messages. When I was testing, I was just manually setting the date. Those expiration dates are set anywhere from several months ago to a few days ago.
The archive rule is set to archive any messages that have passed the Expiration date by more than 1 day.
If you are referring to something else, please enlighten me. I'd appreciate the knowledge.