Im at 42K miles and my JK brake pads are SPENT. researching online, some complain about 15-20k miles per set on the rears. i think im pretty lucky since i pulled 42K miles including offroad and towing use. There wasnt much notice, (grind/squeal) and the back side of the rear brakes were about 1/32 versus about 3/16 on the front side.
Plus side is...my 2012 was SIMPLE to change. it took longer to get the tools out and the tires off than it did to change out the rears. going to do the front's tomorrow. they look to be the same design as the rear. if every vehicle was this easy, repair shops would be out of business.