I'm sure plenty of replacement parts of EOL by decades. Heck, the terminal upgrades alone are likely necessitated by the fact CRTs are no longer manufactured in quantity.
I was running into this doing requisitions for a precision approach radar that was commissioned in the late 60s. By this point, all of the part suppliers had long since moved on to other things or gone out of business, and the usual avenue became "Order the part, and wait for enough air stations to also need the same part. Then, and only then, will the government commission a custom fabrication job to manufacture the parts needed for an obscene amount of money."
Two results happened. First, we ended up paying $15k for parts that were worth $500 because that's what it costs to set up a fabrication job when you only want 50 circuit boards. Second, we did whatever the hell we could to avoid having to spend $15k on a $500 part, and the radar was therefore held together with gummy bears, duct tape, and black magic. It was a clusterfuck, and we were always putting out fires with that thing, sometimes literally.
Horrifyingly, the military has never been able to create a better PAR, which is why it's been around for so damn long.
I got out in 2014, and last I've heard, they just re-extended the EOL for the radar to 2025. They'll probably be sending out lance corporals with binoculars and walkie-talkies to yell "TOO HIGH" and "TOO LOW" by then.