Alternator failed at 370,000, due to dunking in a large mud puddle.
Headlight globes failed due to same mud puddle.
Cylinder head blew at 375,000 km, and was repaired for $1500 with the head re-welded and machined.
Aside from general maintenance, the Patrol has been generally reliable. The cylinder head gasket blew due to a dodgey repair by the previous owner, but aparently patrols on LPG have a bit of a history of warping cylinder heads as well as blowing gaskets.
Have done plenty of miles in the car and cannot fault it. The majority of things that have gone wrong are my fault (due to offroad use in flooded rivers), and the car has only once let me down (head gasket). In spite of this, the gasket repair cost less than a factory service of my TD5 landrover at 30,000 km.
For offroad use, I would recommend a 2" suspension lift, as the chassis is lower than most other 4x4s, and good tyres are essential as this is a heavy car (2.6T fully loaded for a week camping).
All in all, the most reliable and easily repairable 4x4 available.
I own a 91 GQ 4.2 LPG/Petrol, I've had since 1995. Now with a family it's getting a bit squashy on those camping trips in a short wheel base GQ. I have held onto it because it has been a great vehicle, it has racked up 470,000km and it is a pleasure to own. No major mechanical problem, still running original head and motor. The only con is heavy on petrol, but is o.k. on LPG.