FFfffffffff.... Dang, there's a really good movie about something like this, but I forgot the name. Aaanyway:
1. I may not age, but I may be mutated. I mean, if there's a gummy bear that can give me immortality and it came from the future, there's certainly something that can keep me up with the times.
2. After a dozen of years I can just move to a different place, not necessarily far away, and after every few dozen of years I could pretend to be my own son.
3. If my body isn't aging, than it's only natural to assume my brain isn't aging either. That said, I don't remember all the bits and pieces of my life, so after 100 or 1000 years there won't be any real reason to remember the things from my earlier life, and they'll fade as I get new experiences.
4. I don't think I'd go insane. Knowing I've got all the time in the universe would pretty much null the whole feeling of time flying by as I've nothing to lose by its passing.
5. Meh, that could be ugly but it's better than not being alive. I simply cannot comprehend death. And who knows, pain being nullified I might be able to wiggle my way out of the rubble, and in case everyone dies it's just a matter of waiting for new life to be born.
So to sum it all up, gimme that candy please!