This is very interesting - and bravo for making something that lasts so long. Can you share anything more about what those machines do and why they are so durable?
In general most older machinery was designed to be repairable. Often using industry standard sizes for things such as motors, bearings, relays, screws, etc. As long as you can get (or make) the parts and are willing to maintain the equipment, you can keep using it.
Indeed. It’s often the case too that it becomes outdated - more modern designs are more efficient etc. I’m probably more intrigued / surprised that it’s economically effective to keep a seventy year old machine working.