While Emacs itself is not entirely immune to software rot (external dependencies and all), it’s truly amazing how little to no rot is experienced by elisp software (packages). If you find an Emacs package written 15 years ago, the chances of successfully running out of the box are incredibly high.
I was thinking the exact same thing. As long as you're not depending on any external packages things are very stable. Like, if you're package depends on adding advice to some other package's random internal function, then yeah, it could easily break.
It's a great feeling knowing any tool I write in Elisp will likely work for the rest of my life as is.
