Procrastination
Procrastination's documented history extends to the earliest human civilisations. Ancient Greek philosophers coined akrasia to describe weakness of will, whilst Roman texts lament the postponement of important duties. This represents a minimum operational lifespan of 2,500 years of documented activity.
The phenomenon shows no signs of diminishment. Indeed, modern conditions appear to have strengthened its prevalence. Unlike entities subject to fashion cycles, procrastination's relevance only increases as societies generate more tasks requiring completion.
The Joker
The Joker's existence spans 84 years from initial publication, a respectable tenure for a fictional construct. Multiple reboots have refreshed the intellectual property, ensuring continued commercial viability. Warner Brothers' aggressive copyright protection suggests continued exploitation for decades to come.
However, the character remains subject to corporate decision-making and cultural relevance. Should superhero narratives fall from favour, The Joker's prominence would necessarily decline. His immortality is contingent upon market forces rather than inherent permanence.