Internet software decays: https://utcc.utoronto.ca/~cks/space/blog/tech/InternetSoftwareDecay
(Software is dependent on the environment, and that's changing! You also have to stay on top of evolving security concerns.)
Related Posts
On thinking of books like software, treating them as evolving artifacts, and URLs versus paper book publishers: https://cs.brown.edu/~sk/Memos/Books-as-Software/
Learning software development through playing and contributing to a MUD: https://tashian.com/articles/how-i-learned-to-program/
I'm a fan of the Software Unscripted podcast, and I particularly enjoyed this recent episode about CrowdStrike and security culture: https://www.youtube.com/watch?v=rzjaZssBEiI
The guest (Kelly Shortridge) compares attackers to lawyers trying to find loopholes. This is such a great analogy.