Since we bought and built on this property 40 years ago, the oldest peony on the site is. . . . 39 years old. Of course, it was taken as a division from the ones in my mother's yard. Still, those weren't more than 10-15 years older. Then again, her's were transplanted from a friend's house. I have no idea how old the original plant might be.
Post again when the flowers are in bloom. I love peonies!
I once read that a plant can only grow so long until it is genetically programmed to die of old age. I pooh poohed that idea when he suggested that all the cuttings and starts from that same plant would die at the same time -- all being genetically the same. I have more faith in the Master's plan than that!