Ever wonder why turtles live so long?

From here:
http://www.slate.com/id/2138560/?GT1=7850

Why Do Giant Tortoises Live So Long?

They're big, they've got armor, and they live on an island.
By Daniel Engber
Posted Thursday, March 23, 2006, at 6:36 PM ET

A 255-year-old giant tortoise named Adwaitya died at the Calcutta Zoo on Wednesday. The animal had been brought to India from the Seychelles Islands in the mid-18th century as a gift to the British colonial ruler Robert Clive. Why do giant tortoises live for such a long time?

So they can reproduce more effectively. Long life spans provide an evolutionary advantage for certain types of animals. It makes sense to stick around if you live in an unpredictable or harsh environment where it's hard to reproduce on a regular basis. (Desert animals, for example, tend to get quite old before they die.) You'd also want to have a long life if you could only give birth infrequently for some other reason, or if you spent a lot of time caring for each of your offspring.

Every species has its own "life history," or schedule according to which it passes on its genes to the next generation. Some animals invest their time and energy in having lots of babies while they're young; others use their resources to live longer. An animal might live fast if there are lots of predators around—if you're going to die young, you might as well get the baby-making over with as early as possible. (This strategy works only in a predictable environment, where you know there will be enough food around to feed all your babies.) The long-lived animals, on the other hand, have often evolved some way to protect themselves from predators.