It's at the point now, because so many of the old 4wd's I would consider buying are getting so long in the tooth, that I wouldn't buy them even if I could afford them.
I disagree. The older ones are generally a lot easier to work on - less complicated systems, especially electronics - to work on. General the parts are still available and easy to source and generally cheaper than modern equivalents.
As long as they are maintained they work great, no different than needing to maintain more modern rigs.
The best example I can give, to the chagrin of my father, brother and father-n-law, is this. I have a '63 SIIa 88 Rover. It's engine is the original 2.25l 4-cylinder. At the time my brother's truck was a big honkin' heavy duty Chevy 4x4, dad's was a Chevy extended cab heavy duty work truck, the father-in-law's was the lightest of the three but still a heavy duty extended cab Nissan.
The father-in-law and I had rented a rather large cherry picker to to trim some trees at his place and ours. The first night we had it at our place there was a freak rainstorm and were the thing was parked became a bog. Along with that the tires were up against a slight rise in the yard (almost like a tall sloping stairstep, about half the height of the cherry picker's tires).
My father-in-law hitched it to his truck; it barely moved and just wedged the tires closer to the slope.
We contacted my father and be brought his truck over. Same scenario.
My brother was about to go off duty at the local firehouse so we contacted him. He came by with his truck, the biggest of the three. It's been heavily altered because it was used as a first responder unit as well (small towns can get by with this).
We were all surprised when his rig didn't pull it out. His actually wedged the tires worse AND tore up my yard.
At this time the three of them were discussing alternatives, such as a local tow truck as well as pulling it the other direction.
I suggest the Rover - and they laughed. They said it was too old and too under powered.
While they continued debating what to do I got Grover and hitched the thing to him.
While hitching it up they scoffed.
Before I continue... the Rovers have a "high" gear and "low" gear. In low gear you're automatically in 4x4 (just need to lock the front hubs). You can also go into 4x4 while in high gear. Back when Grover was made there was an option available that most civilian Rover owners didn't opt for but Grover had - a lower gear gearbox. Basically, Grover's "high" gear was the equivalent of the standard "low" gear. These gearboxes were intended for the military or for heavy duty civilian use and were popular with the long range overlanding/expedition crowd. For the time period they weren't cheap.
Anyway, I locked the Warn hubs and put Grover in low gear. I could feel when the cherry picker's tires made contact with the slope; there was a slight hesitation and then the sucker rolled up that slope as if it weren't there.
My father, brother and father-n-law just stood there gobsmacked.
Long story short...old doesn't necessarily mean long in the tooth.