SciFi author Ian Banks 's culture series explores a future civilization where people is potentially immortal but in that society it happens that lots of people lives 150 / 200 or 300 years an then they choose self termination.
Rather than achieving true immortality through some one-off miracle pill a la Golden Age pulps, "immortality" is a sequence of stopgaps - one life-extension therapy gives an individual enough time for science to advance to the point where it comes up with another extension. Rinse and repeat for eternity (or until your nanotech goes crazy and melts you from the inside out, whoops).
The sociological consequences of a system like this, where maintaining your immortality through the pursuit of enough wealth, prestige and tech to get your hands on the hottest new therapies becomes practically a raison d'etre in and of itself, are an interesting contrast to Banks' utopianism. I'd love for us to go Culture, but I'm not holding my breath. On the other hand, I wouldn't be surprised to see some variation of the therapy-chain thing during my natural lifespan.
It's interesting to note that he also wrote some about the style of immortality described by Alastair Reynold's and the cheap immortality of his "Known Universe/Ringworld" novels is after that time period in which longevity has become cheap, commoditized, and easily affordable by all.