Reddit mentions of Starlight Crystal

If "until the end of the universe" counts as "forever", check out The Starlight Crystal by Christopher Pike. It's a YA novel, so even though I remember really liking it in junior high, YMMV as to how well it holds up. Same goes for The Ellimist Chronicles which will probably only make sense if you're familiar with the Animorphs series.

If you're willing to accept side characters rather than protagonists, there's Wowbagger the Infinitely Prolonged and Marvin in The Hitchhiker's Guide to the Galaxy, as well as Anne Poole in Fine Structure.

And if you're interested in movies with this theme, you might like The Man from Earth.

Starlight Crystal?

http://www.amazon.com/Starlight-Crystal-Christopher-Pike/dp/0671550284

This is also a plot of a novel I read for school. "Starlight Crystal"

https://www.amazon.com/Starlight-Crystal-Christopher-Pike/dp/0671550284

I sort of create a soundtrack of sorts in my head when I'm reading a really good book. For example when I read Christopher Pike's The Starlight Crystal I thought that if they made a movie out of it, one of the main songs on the soundtrack should be savage garden's To the moon and back