Books will last much longer than that. Their most common mode of destruction is storage-in-landfill. Moisture (may that be flooding or mold) and fire are the main environmental factors diminishing the lifespan of a book. Things such as the acidity of paper are only an issue for book collectors and libraries. That leaves wear and tear, which can usually be repaired. In other words, books are more than capable of lasting for the lifetime of the original purchaser.

Now contrast that to digital downloads with DRM, where you are at the whim of the vendor. The worse example I've seen is a perpetual license expiring after 2 years, though I have lost access to several hundred dollars worth over purchases over the past decade (and I'm not a big spender).