hahaha you're hilarious. get the 4th gen reactors running, introduce the thorium fuel cycle, and we have millions of years of fuel. what the hell kind of zero growth steady state weirdness do you subscribe to?
the sun will eventually die out too. i can't believe people say things like that.
get to the moon, mine the He3 there, and upgrade our power facilities to fusion, it's much more efficient anyway. we can use the he3 fuel to get to the outer solar system that is the essentially the persian gulf of fusion fuel in the gas giants... then at that point we must leave the solar system, because as you pointed out, all things must eventually come to an end, and to protect our species from a system wide eradication such as a GRB we must expand outward.