The Quest To Find the Longest-Serving Programmer (tnmoc.org)
In 2014, the National Museum of Computing published a blog post in which it tried to find the person who has been programming the longest. At the time, it declared Bill Williams, a 70-year old to be one of the world's most durable programmers, who claimed to have started coding for a living in 1969 and was still doing so at the time of publication. The post has been updated several times over the years, and over the weekend, the TNMC updated it once again. The newest contender is Terry Froggatt of Hampshire, who writes: I can beat claim of your 71-year-old by a couple of years, (although I can't compete with the likes of David Hartley). I wrote my first program for the Elliott 903 in September 1966. Now at the age of 73 I am still writing programs for the Elliott 903! I've just written a 903 program to calculate the Fibonacci numbers. And I've written quite a lot of programs in the years in between, some for the 903 but also a good many in Ada.
As someone with only a measly 20 years of experience can attest. The code from these indispensable people, are really not that impossible to take over, especially after these trouble makers leave and they don't actively work to stymie your investigation and mapping of the code.
Bad programmers make code that you think you need to keep them hired.
Good programmers make code that you want to keep them hired.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.