&gt; He stared writing the compiler being almost thirty years old. That means at the time when his programming abilities started to decline.<p>Citation needed. Even accepting the results of various studies that show age-correlated decline in some measures of programming ability, one cannot take those results and conclude that a specific programmer&#x27;s ability began to decline at 30. Also, AFAIR the studies don&#x27;t agree on a specific age and report increasing variance which makes it even less reasonable to make the conclusion the author made.