friend of mine has nearly the same truck but in crew cab and a 4" lift, he gets about 14mpg and drives it right at 100 miles a day during the week. It has like 90k miles on it, and i dont think he has replaced any balljoints or wheel bearings yet.
I get 12-15mpg with my 35's and programmer. The extra 4" of height on that will probably take a little more fuel. You should be good to go for a while regarding bearings/ball joints. I think the more common one is the upper balljoint, but it is an easy fix and should be good for some time.