If using the expired CO pass at a CO club, you should be alright. While it is up to the agent, most of the time CO will accept their own. I was shot down once at a NW Club because it was expired, and at that point the club agent said go ahead before she realized the expiration (3 months expired).

In 2001 or 2002 (can't remember), I used an expired PC pass in the CO club at ORD without any problems. That pass expired in 1999!

So go for it and let us know how your outcome is!