I usually buy the lowest fare class available, and I know that those fares change a lot over the course of a few months. But I am in the position where I need to buy a couple itineraries in a W-class fare (one for the ORD DEQM promotion, and another to use some SWUs). Do the W-fares vary as much as the lower classes? Or are they pretty static? Same would apply for Y/B fares, or any other "higher" fare class. I ask because I could buy the tickets now, and save me from worrying about it. But if the fare may drop significantly over the next few months, I would wait and see. Thanks!