If we ever manage to find a way off-planet, being able to live for half a millenium (or "forever", or until-I-decide) sounds AMAZING.
It does sound like quite the economic problem, though, and would certainly make earthbound resources more troublesome.
As for the environmental issues and being selfish, this doesn't have anything to do with how long you live, but rather with how you live. Obviously, a society with life expectation that is so long would have to reduce the birth rates substantially (or, rather, keep them the same in the births-per-lifetime department). But if you can do that, then there's no reason why it's any more straining on the environment, whether its 1 person living for 500 years, 5 people living for 100 years each, or 10 people living for 50 years each.
You could say it's "selfish" to live one life where there could be ten, but how can one be selfish with respect to non-existing persons? How is it different from someone being "selfish" and not having children, for example? And why wouldn't it apply to ourselves with our current lifespans? Why not, say, euthanize everyone at 30, and use the existing resources to sustain more short-lived people, if the number of people having lived is the metric?
It's more selfishly using the resources younger people can use. If you're eighty, I'd rather feed the eight year old. Until we move beyond resource constraints (lol) this is going to be a major effect of the rich being able to afford long lives AND food and the poor affording neither.
If they sit around doing nothing but eating and playing video games, that would be a waste.
