That was impressive to Rarity. Unicorns lived an average of seventy, with Pegasi and Earth Ponies barely making it passed their fifties or sixties. It was always assumed that the more 'athletically inclined' pony tribes were shorter lived because of the physical toll their livelihoods strained their bodies. Whereas with Unicorns, they were more susceptible to diseases of the heart or brain because of their lack of physicality and excessive reliance on magic. 