I find the 85 to 90 percent hard to believe. I've been selling production equipment for over 30 years. If machines are maintained on a regular basis they can last a long time. Granted some have better bones than others like the Hall lifts that are running after 60 years.
We also rebuild and upgrade older machines to today's standards at a much lower cost than new. If the towers on chair 5 are in good shape a new drive terminal and controls would likely put it good shape for years. Spare parts for Hall lifts are still readily available. I agree those chairs are uncomfortable so they could also be replaced.
Chair 2 is a Frankenlift that just needs to be replaced. It's likely hard to find spare parts for that lift.
You would know better than me with your heavy equipment background. That's a bit out of my toolshed. I just thought the statistic was interesting, as you can keep anything going forever as long as you maintain it. Chris Diamond spent his career in the ski industry starting with Preston Smith at Killington. He ran Mount Snow for a number of years and then ran Steamboat. Before he retired, he ran Vail's mountain division. He also published a couple of ski industry books.
It would be interesting, as an example, to see how much money was put into lifts like chair 2 over the years to keep it running (chair replacements, drive replacements, grips, etc.)
I couldn't locate a digital copy of Chris' article but did find this one from 2015 that places a lifespan of a high-speed quad at 23.8 years. Granted the article is eight years old, but an interesting read.
https://liftblog.com/2015/09/21/the-lifespan-of-a-high-speed-quad/#:~:text=If you figure the average,machines will be in 2022.