My 1999 (bought new) is still adding up the miles, now through 420,000.
The valve covers have never been off, it's the original motor, transmission, diffs, X-fer case, etc. etc. and does not burn a drop of oil still! I'll change routinely at 5-7,000 miles, conventional oil. For mods, almost none except K&N air filter forever, good tunes and nav, and 2" ARB lift along with vented and drilled rotors (which don't warp when all others did from my towing). I don't use premium gas except when towing boat.
Recent work includes new BFG K02's tires (they wear like iron and overall are superb for the LC), ARB/OME shocks and springs, and new CV Joints/Axles after boots finally wore. Lesson, don't bother with aftermarket or re-mfg'd CV joints/axles, they immediately sucked and vibrated at speed, had to install factory, didn't do my homework. Expensive mistake. Time for re-upholstery of front seats.
Truck has had the usual water pumps, a radiator, alternator, a few ignition coils, an AC compressor, a steering wheel and shift knob (both wore) and bulbs but nothing major to date.
It routinely tows a 3300 lb fishing boat and toy trailer, does several major trips to the remote high desert, and launches in salt water without any signs of corrosion for the wheels and rear end that gets wet.
Just an amazing vehicle. Exceeds all expectations.