Technically, yes, it is the "same" clay as they do store it year after year. Some of it came from the original Tulsa Fairgrounds track (adjacent to the Expo Center) which dates back to the 60s. But again, technically speaking, most of this clay dates back centuries if not eons (in nature), so I don't know if it really "wears out". Pretty sure it has more to do with how deep you put the water, how loosely/tightly packed the clay is and how dry the ambient air is. No surface winds to deal with, no sunshine to deal with, no big wings pulling the moisture off the track, so it's really pretty predictable compared to an outdoor track.

Hanging out at the Freeway Cafe a couple of years ago after the Saturday finale and Emmett was holding court. He was most excited about "finding" some new clay to add to his stock. It's a science and a passion for these guys.