Originally Posted by curbcrusher
Given WN's very customer-friendly change policies, I wouldn't worry about when to book. If you need to book a trip, and the fare is reasonable, do so. If you see the same flights available for less later, cancel and rebook (pocketing the difference as a credit to be used later; you mention you fly TPA-BWI often) as described in the FAQ.
Easier to travelcernter -> Change and "pocket" the savings than cancel & rebook. That way if it's the last seat you'll know before you "cancel" what you have.
But to the OP, seats are limited, you mave have seen the last seat at that fare, and when retuned obviously someone else grabbed it.