I have a '12 Sahara and had 3:21 gears in it while running 2.5" and 33" tires. Ran it like that for about 5k miles. I live in colorado so mountain driving up and over passes was tough to even stay above 55mph with pout revving at 4-5000 rpms, the engine would heat up and I would have to let off. Driving I town was bearable. Offroading, forget it unless you are in 4low, zero power in 4hi.
I regeared to 4:88's and jumped to 35" tires. I did 4:88 because I do plan on 37's in about a year after new driveshafts, flat fenders, sleeve gusset, ect. I wanted to just do the regear once. My 4:88's run about 2700'ish at 75mph, but I really jump gears back and fourth - it takes a pretty big hill to do so. If it does jumpmill rev to 3500 rpms, which isn't bad. With the 3:21's I would go to 5000 rpms, felt like it was going down to 3rd or 4th gear, instead of 5th when I would hit a hill.
Regear to 4:10 or 4:56 if 35's is as big as you'll ever go, or go to 4:88's for 37's if that's in your plans.
Also, gas mileage on a 1600 mile trip from Denver to Texas over Xmas I averaged 15mpg. That was all highway, with a jeep loaded down with luggage, gifts, guns and ammo, you name it. I was pleasantly surprised it did that well.
Pics for you to see my '12 with 35's and many additions