Also you might consider the Pro Comp Xtreme MT, the new Dick Cepek MT, or the Cooper STT. Cooper makes these as well as the MTZs. PM Walking Eagle He has about 20k or more on his MTZs.
About 22,000 miles on them. They look like they'll make 40,000 no problem. They've gotten a little noiser as time has passed as I do have a little bit of chunking. But I wheel at least once a month, sometimes more, I'm not nice to my tires, I never got the truck aligned after my 3" lift with MAF drop brackets, and they've worn great for a MT as far as I'm concerned. Been super thrilled with them on ice and snow, which we actually got a bit of this year. Wet pavement traction is great. They ride great. They go through mud great. And they've held up well to the rocks around here. Our rocks are probalby closer to the sharp pointy nasty Lava rocks in Idaho than to the smooth slick stuff in Moab. For the price I paid for them, I couldn't be happier. Well, I'd be happier if they were a full 35"

Otherwise, really, no complaints.
If anyone is really interested, I can snap a shot or two of what the tread looks like now, and how deep the lugs still are. Really, I think 30,000 miles with still good tread on an MT is great, and like I said, they should run 40,000+ before they have to be replaced. What I'm saying though between 30 and 40,000 I'm guessing tread depth will give closer to AT performance off road. Sort of like having a bogger with only 1/8" tread left, they're usable on the street, but aren't going to pull you through the mud no matter how agressive they were when new.