I concur that the PQ is a snapshot in time and may degrade in the slab. I'll tell you another thing that may degrade in the slab, the press. Creases that were pressed out,especially on the spine, can return. So you may buy a 9.4, put it away and never touch it, and it degrades into an 8.5 . This especially happens when the book is not real snug in the well. Not fun. I'll take the integrity of a White Page designation over a manufactured grade anytime. Unpressed, original books with White Pages will someday be rewarded by the marketplace.