There are some remarkable similarities between complex (earth-based) entities that are known for their longevity, like turtles, lobsters and particular trees (and the artificially lengthened Bonsai.) You see a large surface ratio of hard shell or skin, a low ratio of frilly nonsense like fur, leaves/needles or hair. I would posit that toughness-beats-all in evolutionary longevity, and the more we do to strengthen our 'shells' the more luck we'll have. We're at a disadvantage, having bones on the inside as we do.