Death
Death has maintained a perfect operational record for approximately 3.8 billion years on Earth alone. No organism has ever received a cancellation notice or experienced Death failing to arrive. The phenomenon requires no maintenance, never experiences server downtime, and operates flawlessly across all conditions. Death is, quite simply, the most reliable system ever observed in the natural world, functioning with an efficiency that would make Swiss railways envious.
Spongebob
SpongeBob has aired continuously since 17 July 1999, surviving the death of creator Stephen Hillenburg in 2018 and multiple network reorganisations. The programme has produced over 280 episodes without permanent cancellation, demonstrating remarkable staying power. However, SpongeBob requires animation studios, voice actors, and broadcasting infrastructure to exist. His reliability depends entirely upon Nickelodeon's continued financial interest.