Re: none of your code still running in 2100
Depending on what kind of embedded systems you’re building, that may not be true. Stuff like railways comes to mind. 75 years is old, but not out of the question. I believe parts of the NY subway signalling go back to the 1930s.
"And should any of my code still find itself being used by other engineers by then, and should it then cause them to run into Y2100 issues, more fool them for not paying attention to the clear comments in said code explaining the short-cuts/limitations/optimisations/etc taken..."
I worked on railway software that was still in production 30 years later. By then, they had lost the source code. Undeterred, they built a PDP-11 emulator for it (not that the non-standard pre-ANSI C would have compiled as was). It was finally retired when enough new railway stations had been built that a statically allocated array was now too small and it couldn’t load its data at startup! And yes, that array bound would have been #defined, but without the source code...
Someone trying to restore a car or electronic toy in 2124 also won’t have the source code.