After finding a lot more Advantage Level cards from the Horizon Casino in Late Tahoe it's apparent that the expiration dates when present on these cards was printed by the card manufacturer. So I've added the known expiration dates for each issue (6th thru 8th) with scans of all the cards I could find. The 6th issue appears to be complete but there would appear to be some missing dates for the 7th and 8th issue cards. If you have any other expiration dates I haven't listed once you see the new guide or the updates on the ChipGuide after tomorrow, please submit scans or send them directly to me to get them added.
Here's a couple of examples showing the expiration dates on blank cards