Life span of a ding

[DanenRox]

When SWA dings down an airfare, does that fare stay open that rate until the ding time is expired, or until Southwest sells a certain number of seats (then it would become "not available")?

 

[we're all mad here]

Last month, I booked 3 tix on SWA Ding from CLE-BWI for $29. Then when I went to book 2 more shortly thereafter, it showed that the same flight was unavailable for the ding price.

I would guess the ding is limited by seats first then time.