Actually, I always had a different take on Alicorn lifespans.



Alicorns normally have an extra fifty years of life than the average Equestrian, but Celestia and Luna were exceptions because of the Nightmare Moon Duel. the Elements or Harmony put both of their lifespans on hold. They would both still live to see each other again eventually, but neither of them would age. They had to wait until Luna was reunited with her sister. Celestia had to endure a full millennium of isolation from family to keep countless generations of Equestrians protected. It doubled as a gift and a curse, due to the energy of the Elements AND Alicorn magic keeping her around for longer than any Equestrian would have expected. Because of Celestia's long lifespan, people considered her to be very much like a living Goddess.



She counted down EVERY day until it was time to say hello to her sister again. She wouldn't make the same mistakes.