Being only a casual fan of the material (I read the book in school and have never seen the movie), I was taken by surprise at the level of demand for the show. I finally went looking for a ticket last month, and couldn't find a decent non-premium one until March.
The advance of $22 million is certainly one of the highest for a play in Bway history.
In most recent years, there's a lull in September where there are often no plays running on Bway, the star-driven vehicles from the spring having finished and before the new season's plays start. But between this show and Harry Potter, that may not be the case for many years to come.