1) I was tasked with instrumenting the T58-GE-16 engines in a CH-46 [0]. So what did I need to inform my sensor placement and selection? Some schematics and technical manuals, all from the late 1960s, all undigitized.
2) I needed to reverse engineer an old test set. The documentation had been lost to time. When I cracked it open, I saw lots of 5400 & 7400 series chips. Now, this is kind of a trite example, because lots of working EEs still have copies of the TTL Data Book at hand. But still, I needed to refer to that old tome when working on this project.
3) When I worked at a NASA contractor, a primary piece of equipment failed. We needed a replacement in a hurry. Fortunately, someone had kept the older version of this system around. It dated from 1959 (!) but the manual was still around, too. A quick read through that manual got us back in business.
Technology never dies [1]. But without the manuals to understand that technology, things become much harder when you need to use that technology again.
[0]: https://en.wikipedia.org/wiki/Boeing_Vertol_CH-46_Sea_Knight
[1]: http://www.npr.org/sections/krulwich/2011/02/04/133188723/to...