The successor IBM Mainframes are still alive... for the time being.
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When I was growing up (decades ago, mind), my dad kept trying to convince me to get into machining. Lathes, mills, tool and die making, etc. In his line of work, he saw lots of machining companies basically paying all education and training expenses for new hires because their experienced old timers were retiring faster than they could be replaced. (He also thought computers were a fad...) I'm sure it was a good opportunity at the time. But nearly all of those companies eventually closed up because offshore manual labor was and still is way cheaper. If I'd had taken his advice, I'm pretty sure I would have had to reboot into another career at least once by this point.