Panda
The giant panda lineage extends approximately 8 million years into the evolutionary record, a respectable tenure by mammalian standards. Individual specimens achieve lifespans of 20-30 years in the wild, with captive pandas occasionally exceeding 35 years under optimal conditions.
However, this apparent durability masks a precarious reality. The species teetered on extinction's precipice throughout the 20th century, with populations dwindling to fewer than 1,000 individuals by 1980. Modern conservation efforts have elevated numbers to approximately 1,864 wild pandas, yet the species remains classified as vulnerable.
Time
Time's curriculum vitae regarding longevity is, quite literally, unimpeachable. Emerging simultaneously with the universe itself some 13.8 billion years ago, time has maintained uninterrupted service without pause, holiday, or maintenance window.
Unlike the panda, which required external intervention to prevent extinction, time has never required conservation efforts. It cannot be endangered, protected, or preserved in reserves. Time shall persist long after the last panda has shuffled off this mortal coil, continuing its relentless march until the heat death of the universe renders such measurements meaningless.