I think the biggest tires you can run without cutting your front bumper is about 32-33". I have 32" tires and they fit fine, but do rub on the fenderwells if I hit a bump while turning. With your 2" lift you can probably go a bit bigger, though. Someone else should have better info for you.
I believe the tire width hurts mileage, taller tires can theoretically help mileage if you have a soft foot. Although tuning makes a bigger difference than tire width, IMO. Remember, tire compound and tread pattern makes a difference in mileage just as much as width. And of course, driving with a light right foot will save you the most gas. And since your last tires are burning up as quick as they are, I'm guessing you aren't easy on the skinny pedal.
As for tire life, I can share our experience with various BFGoodrich tires. I am happy with my BFG All-Terrain tires. I have 40,000+ miles on them now, and still 25% left. However, we have gotten as little as 12,000 miles on a set, when towing heavy with a heavy foot. The most we have gotten from a set of tires is 70,000 (and counting) from a set of BFG Rugged Trail tires. They aren't as aggressive, and you get stuck easier off-road, but you get great tire life and pretty good gas mileage (better than the All-Terrains).
If you are looking for mileage, run the tallest, narrowest tire you can find, and preferably get a LRR (low rolling resistance) tire. However, that setup won't perform well off road, and probably will look kind of lame. Plus, you'll fry them off at the drop of a hat, which could negate all the savings in mileage. It is all about finding a balance you are happy with. For me, that is BFG 285/75R16's, but I'll probably get the 295/75R16's next, as I need more traction
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