It's going to depend on the book and how popular it is. Some sell out relatively quickly, while some still have copies in the warehouse years after they are released. (Hardcover books are usually "evergreen" products and will be reprinted if they sell out, with the notable exception of the AP compilations.)
Paizo periodically list their products for which supplies are dwindling, and they actually just did so at the end of December so you can see which products may soon be unavailable.