All wheel drive constantly uses the front wheels... most of the time you were driving in 2wheel drive in your jeep. It's important if you want your truck to last. You should especially do it if you dunk the front axles in water... otherwise I'd say you could wait maybe 30k between changes, IMO. My brakes last about 70K.. so there's no way I could ever wait for a change... but it while you're doing the brakes, you have to repack the wheel bearings (unless you just change pads).. so it depends on how long you have to wait. Maybe it's better to do the brakes now and the wheel bearings. I do the bearings myself for around $40-$50 now, in about 3 hours. (something ALWAYS happens, forgot grease, had to order seals, blah blah) should only take 1.5 hours or less...