Immortality means different things to different people. My favorite mental game along these lines is to try to imagine the ramifications if eternal life doesn't include a better memory. I look back 20 years and think "oh yeah, I used to know a lot of statistics and calculus and French." And the thing that bothers me isn't that I no longer know those things, but that I rarely even remember that I knew them. In a hundred more years, would I have forgotten all my childhood friends? You bet. Ex girlfriends? probably. My brain in a hundred years would make for a thoroughly goofy personality. In a thousand years I wouldn't be even identifiable as the same person. If I am not mentally the same person, is there any point to keeping the body alive forever?