Like any sales strategy, if you use it too much, it becomes less effective. Also, I think there’s something to the notion that we’re well past the point where any regular person can afford to pick up every last appearance by their favorite character–the books are simply too expensive for that. Couple that with the fact that every story we do is now likely to be collected elsewhere, to say nothing of available perpetually in the digital format, and the drive to read every single story of a favorite character as they come out simply isn’t there in the same way–there’s always time to get caught up later if something key happened somewhere else.