There's a number of Evo bikes around here with around 100,000km (60,000 miles), mostly touring bikes, both 80 and 88s. There's some good deals to be had and I'm tempted, but what are the risks of an engine with that kind of mileage?
The EVO can last as long as you want it to. Just keep it maintained!
With the Touring bikes....saddlebag hinge hardware/tourpack hardware fail.(missing nuts and bolts from miles and vibration) As the bike ages...wiring can be a real PITA. (cruise, radio, EFI stuff, lights,etc.) More stuff you have....the more stuff can and will go wrong.
It's not the engine to be concerned with....it's all the other crap on the bike.
Yes, saddlebag hardware is a pain in the ****. I bought 1988 Electra Glide with 78k miles, four years ago. No major problems with the engine. Just replaced piston rings, regrinded valves and put it back together. Four years and she`s still running great.
The first thing I would investigate is when if ever, the lifters have been changed. I had a lifter self destruct and take the rest of the motor with it. The cam bearings should also be swapped while your in there. That alone will save you a big head ache.,,