Firstly the sun isnt changing very fast at all, It takes millions of years for a sun to go through all its stages until it eventually collapses into itself becoming a neutron star or Black hole. Next if people can eventually have the abillity this poses many large problems. On a small scale the thought of being able to live forever may seem appealing, but at the current rate we Reproduce, We will over populate our planet far more quickly than our Technology can advance, This would mean over crowding, mass pollution etc. further more, even if we have the abillity to travel through space, finding a liveable planet is definatley not as easy as it seems. There are many exact specifications which we, the people, and the various other types of species living here need in which to survive. Another problem is that if we cure ALL diseases this will further contribute to the over population of the planet I.E. Diseases are natures way of population control, along with natural disasters. The only other way Human populations are controlled is when war occurs, and the next war we have WILL most likely end civilization as we know it. This is because the next war won't be Guns and Tanks, but rather Massive Nuclear weaponry which will destroy mass ammounts of people. An example would be when he set off our first Nuclear war heads in Hiroshima and Nagasaki back in WW II, Those war heads killed thousands, but compared to todays standards of nuclear weaponry they are considered rather small and weak war heads. I imagine that society will not be whiped out by the sun exploding or anything of the such, but rather Society destroying itself, whether it is through war, Corruption, Over-Population, or many other things that come along with "civilized man". It is only a matter of time before Civilization as we know it Implodes on itself, leaving nothing but the smoking remnants of a formerly great People.