Even if they can plausibly survive for 300 years, that doesn't change how lame it would be. Geeze, even Luke Freaking Skywalker died at some point.
"Grant Allen [...] had written a book about the Evolution of the Idea of God. [...] it would be much more interesting if God wrote a book about the evolution of the idea of Grant Allen." ~ G. K. Chesterton, The Everlasting Man