Honestly. In terms of living out of it for 3-4 nmonths you're looking at some interesting compromises. You're either going want a rig like the Comander (or and older Grand Cherokee or Wagoneer)for the room to live out of or something like a Wrangler if you want trail performance. But you're really not going to find both unless you went with a ZJ or an older Wagoneer. The Wagoneer with a Diesel swap would be a great Expo platform IMO.
OF all the Jeeps out there, and for my load/people carrying needs (or lack there of) the LJ (2 Dr. LWB unlimited) Rubicon would be the best IMO. Perfect wheel base, more room to carry things, solid axles, lockers etc. But it's not too big and honestly I'd be hesitant to "live" out of it for many months on end. It is however very capable off road and with the added WB rides quite well on the hwy. too.
On the other hand, out of Jeeps new vehicles, the Comander seem the most promising in the gear hauling venue. That said, it's nowhere near as trail worthy as the LJ. So there are trade off's. There IS one SWEET Comander here on the board that seems to make a good case for their off-road ability... However it is the exception, not the rule
It is one cool exception though eh.
Honestly Unless you're ABSOLUTELY non-flexible on brand's and simply MUST have a Jeep:I'd simply suggest that there are better makes of vehicles in terms of both the ability to haul gear, handle trail duties, and ultimately (and most importantly) last longer.
Cheers
Dave :safari-rig:
EDit: Honestly... Be wary of "built" Cherokees I say this having owned quite a few, and if abused the uni-body just doesn't hold up in my experience (and experiences vary eh). Plus IMO, and this is just me being non-trusting of people in general, when someone says "built" I just start imagining all of the things the PO did wrong... personaly I'd be looking for something with a good old frame underneath it. PLus in my experience the XJ, as wide and stable as it is, is really cramped inside. It may look like a decent sized truck, but let's just say your back passengers if you have any will hate it after more than a few hours. Some people fit in them very well and comfortably... At 5'11 190lbs (as in not a big and tell person by any means) I foud them, all of them, to be very uncomfortable ergonomicaly... Even more so now that I'm driving the 4Runner.