Why wouldn’t they be? Rail Car’s life expectancy is 50+ years.. you refurb the inside from time to time and rebuild the few mechanical systems on them, but they are very simple and heavy duty, they are supposed to last for 50 or more years.
When I went to High School in NYC in the 1960’s, the old Metropolitan Avenue El had rolling stock from the 1890’s in service. It was the oldest rolling stock in the Western Hemisphere, even the Cubans had newer trains.
They were sparse, but except for the occasional engine fire in mid-August, they ran pretty well.
There’s a bit more to them than that. Door opening and closing systems, HVAC, software, etc. are high maintenance systems. When you get to the motors, trucks, etc. if you get fifty years ... you’re doing fantastic. They are not simple as you as think. If you’d ever seen one built, you’d know. There’s a huge amount of testing involved.
Metro’s big problem was choosing a manufacturer that didn’t have a long history in the business. Even with one of the biggest Bombardier (Adtranz) you’re still making a big leap of faith.
Typically that is a low margin business. Check Bombardier’s stock price pre-Adtranz and post-Adtranz if you don’t believe me. Diamler didn’t own Adtranz long before they dumped it. Metro’s management picked someone even less qualified.
50 years if properly maintained and designed, which the ROHR 1000 series are not. That’s why the 1000 series cars in the 2010 red line crash were demolished and the 4000 series were still in one piece. As far as the maintainance goes Metro can’t properly maintain escalators let alone the cars.