I think life after 80 goes downhill not just because of health but because people you are familiar with and things start going away. Things change so quickly the world starts to become unfamiliar to you. Its like living on an alien planet. I think living to 1000 years would require one to leave the world, do some adjusting/re-education/reworking and then re-engaging with the world again. It would be like every 100 years going back to college and starting again. New friends, new music, new everything so that one could keep going.