Our is a '73. Late last summer we did a 4200+ mile excursion that included Yellowstone. We got 9.2mpg. We had a great time.
There is now one "orphan" part and that is the inner tie rod end (until one of our suppliers talks a manufacturer into running some). Other than that, if you need it to keep the coach on the road you can get it. There is a large support network.
In the front, it rides like a car (actually better than many). In the rear, you can sleep underway if you choose to.
She's asleep in my barn now, over the winter I need to do a lube service on the driveline, lubricate the suspension, clean the carpet and deal with a drip from the potable pump. I do all the work myself: A-because I can and B: because I don't trust anybody to do it right (the same is often true with our newer street cars).
There are well engineered fixes for all the short comings that they were built with and even some to just make them better.
Oh, in 4 weeks and 4K+miles, we broke a drawer slide and I had to adjust the generators carburetor for the altitude.
Though keeping old coaches going?? Not when you keep up with the scheduled maintenance.
A lifelong waterman and his bride going dry places for as long as the fuel money lasts.