Had mine replaced today with the GoodYear DuraTracs.
I drive all country roads and about 1/3 of it has a lot of curves. So although my Terra Grapplers only lasted 31,314 miles, they would likely last someone that did freeway and city streets a lot longer. As a comparison, my Toyo M/Ts made it to 37K miles, the BFG A/T KO's to 33K miles and still had 1/4 of their tread but were unusable on wet roads at that point, and the stock BFG Rugged Trails lasted 23K miles.
I'm really glad to see the Terra's go, and expected much better performance and ride after reading so many positive posts on them, back in '09. They had poor wet traction until I had them siped, but even off road on dirt and loose rock hills, they spun more easily, (non-air'd down), than any tire that's been on my Titan, (not including the DuraTrac's which I got put on today and haven't tried yet in the dirt).
Btw, my Nitto's were getting fairly noisy, down to the wear bars, but I think my new DuraTracs are already as noisy, but they might mellow out after some break in. I think a little tire noise scares off the deer so I don't mind.