> buying a piece of shrink-wrapped software and using it for the next 18 years

I'm wondering how that works. I have written software that was still being used, 25 years later, but it was pretty much a "Ship of Theseus," by then.

Old hardware or emulation of old operating systems on new hardware.

Quite common on old industrial machinery and other capital equipment like lab equipment. San Francisco BART for example has to scrounge eBay for old motherboards that still allow DMA to parallel ports via southbridge because it’s too expensive to validate a new design for controllers.