I'm also curious about one thing. Do waitlists become stale?

I had that 10-month HKG-YVR waitlist T-5 not clear even though seat was available http://www.flyertalk.com/forum/catha...l#post24966618 . I had to rebook it manually.

OTOH I had experience where I create a waitlist for pax B which I already had confirmed for pax A, cancel the itin of pax A shortly after the waitlist was created, and pax B will immediately clear http://www.flyertalk.com/forum/catha...l#post24713062

I also recently had a waitlist for a public holiday clear on me about T-320 (I created the waitlist T-360). The flight is still sold out for new redemptions.

Is there a "freshness" criteria to this?