I am trying the new Nitto Trail Grapplers. A little less aggressive than the Toyo MTs. They have not been out long enough to get an estimate of the tread life, but they are doing okay in the mud so far. I spend a lot of time on the Diesel Truck Resource forum, and people do report 40k or more out of Toyo MTs.
It appears that diesels are hard on mud grips in particular, and it can be a trick to find the size you want in the proper weight range. That is one of the reasons I went with Nitto, available in the 295/70-17 size I wanted in load range E.
