I used to work for Lexus's US HQ. The Chief Engineer for the LandCruiser 80 Series was in a Lexus meeting (as I recall, he was also CE on the Lexus SC/Supra) and I remember him mentioning that the design target for the 80 was to last 250,000 miles in a typical offroad environment. Obviously, this assumes a maintenance program matched to the use.
So, don't figure on yours wearing out anytime soon. Will some components go earlier due to a previous owner's mistake? Sure. The more you personally work on your 80, the more you'll come to understand how there are many little durability decisions that were made throughout the vehicle to achieve that objective. I bought my 93 new and if it doesn't hit 400,000 miles without a major failure I'll be disappointed. I have a brother in law (not to be confused with my brother on this list) who's taken casual care of his 93 and he's got around 280,000 miles on it. I drive it every year or so and have a vehicle development background (Lexus, GM, Toyota) so it's significant that I can discern literally no difference in the way it drives compared to my overmaintained 80 with half the miles.
Here's a micro example. When mine hit 100k, I put fresh factory shocks on it. When I took off the old ones, I cycled them and examined them. None of them exhibited the slightest change in damping or smoothness from the others. I found out why when I first drove it after I put the new ones on. Only the faintest difference, and I have a well tuned butt. A typical owner would likely never notice. So, a lot of component decisions were made in favor of higher grade stuff in addition to the fundamentals of frame, axle and powertrain strength and durability.
I think that most of us will step out of our 80s for the last time simply to get into something different, rather than because it's become an unreliable high mile rig. My brother in law routinely jumps in his and drives thousands of miles on vacations with his family and never gives it a thought. And that thing's never so much as missed a beat in all those miles. They were designed to be continuously maintained in return for hundreds of thousands of miles of use, and the ratio of maintenance:usage stabilizes at around 120k and just goes on and on and on...
DougM