Astronaut
The human body was spectacularly unsuited for space travel, a fact that astronauts must overcome through extraordinary engineering. Without protective equipment, an astronaut would survive approximately fifteen seconds in the vacuum of space before losing consciousness. This fundamental fragility requires constant technological intervention.
Astronauts undergo bone density loss of 1-2% per month in microgravity, muscle atrophy, vision deterioration, and increased radiation exposure. Career longevity is limited; few astronauts conduct more than four or five missions before the cumulative toll becomes prohibitive. The physical demands ensure that the astronaut's prime operational window rarely exceeds two decades.
Monday
Monday has existed in its current form since the adoption of the seven-day week in ancient Babylon, some four thousand years ago. Despite countless attempts at reform, including the French Revolutionary calendar's elimination of the week entirely, Monday has survived every assault on its existence.
The durability of Monday transcends individual civilisations. Empires have risen and fallen, languages have evolved beyond recognition, and entire species have gone extinct, yet Monday persists. It cannot be degraded by radiation, requires no maintenance, and demonstrates zero signs of structural fatigue despite millennia of continuous operation. Its durability is, for practical purposes, infinite.