And it may happen in our lifetimes. We need a gene therapy that adds on more TTAGT (telomere) on both ends of all your DNA. When that's worn off you start dying of "old age."
Next generation, of course, is going to wish for the scientific discovery that keeps people looking young. That's not too terribly tough, either, it just involves collagen. Not injections, I wouldn't think, but a real way to replenish it and prevent it from wearing out.
So, you may live for a real long time, you yourself, but you aren't going to be sexy anymore.
Also, people are going to have to stop being so mean to their livers and lungs if we live a real long time, since the problem solved above was just "old age" and not emphysema or cirrhosis. So, as we live longer, we'll be having less fun per year earlier on.
But the alternative to (eventually) banning alcohol and cigarettes is a lifetime of medical coverage for people who might live forever but who have killed their own body. I think pot will be OK, as long as it is ingested. See: Brave New World.