The economists of the blogosphere are pondering the nature of a post-mortal society, an activity that strikes me as thinking hard about what to do with the pits before you've planted the cherry tree. A great deal of work lies between here and there - we are barely starting on the serious effort to defeat aging through medical science.
The basic consequences of living longer are fairly straightforward, in the economic worldview at least: your time preference extends outwards. In theory that means that individuals are increasingly less likely to trash the future for the sake of the present; a long time preference looks a lot like wisdom when seen from the side. What that means for a society of like-minded and very long-lived folk is anyone's guess; no simple trend in individual averages extrapolates out to group dynamics. But it seems to me to be the case that the last factor of two increase in life expectancy produced changes in human society more remarkable for their subtlety than anything else.
Or at the very least, it's hard to pick out what is longevity versus other technological advances and wealth creation.
If aging were curable, would people feel less inclined to expand government?
These days, I tend to think of the issue of the size of government as essentially a power struggle between capitalists and anti-capitalist intellectuals. I don't see how a cure for aging resolves this conflict.
If an ageless 150-year-old behaves like an old person, then he or she will have a goal of stability. That might mean a very non-libertarian attitude. But I am not sure that ageless people will have attitudes that are elderly or not.
If we assume monotonicity (and why shouldn't we?), we can draw inferences from societies with short life expectancies. They are extremely superstitious, willing to entertain tyranny, and hardly libertarian. Try teaching Henry Hazlitt in the Congo. More generally, pending death makes us think of honor, patriotism, and in-group solidarity.
Immortals would have far more to lose by dying in an accident than the average guy who kicks the bucket at before passing the century mark--particularly so, since the immortal never experiences age-related decline--which will make them far more risk averse. Risks that seem quite tolerable to normal human beings, like driving on the freeway or allowing aircraft to fly over your house, will be completely reckless (even insane) to an immortal.
Put more effort into making longevity medicine a reality, and increase your chances of being able to debate this sort of thing for as long as you care to. Not to mention living to see what a post-mortal society actually looks like. From where I stand, that's a much more interesting brand of economics as human action.