To be honest, there are three possible answers for me.
First off, blank. No one should have to life forever. If I left it blank, everything would be normal.
Second, there's a number greater than any normal human, somewhere around 200. With this, I could do much more good in this world than any normal human without fear of death.
The final answer though, is the most painful for me to say. Infinity. As has been said, even by me, nobody should have to live forever. But with infinite time, you can do good until the universe runs out or at least until your sanity does. I say Infinity not because I want to live forever, but because it could help the world. Of course, there's always the theoretical possibility that the human race could go extinct, but there's also the idea of making things right.
Of course, I would probably go with option 1. It just seems morally correct.