In Sid Meier's Alpha Centauri (SMAC), Clinical Immortality is a Secret Project. It may be built at a cost of 450 minerals, on discovery of Matter Editation (B12). Clinical Immortality makes one additional citizen into a Talent at each of your faction's bases, and doubles your vote in Planetary Council elections for Planetary Governor and Supreme Leader.

How useful is this? The Paradise Garden base facility makes two citizens into Talents at the base where it's built, so Clinical Immortality is similar to getting half a Paradise Garden at each base. A Paradise Garden costs 108 minerals to build, so Clinical Immortality is a pretty good deal at about the cost of 4 Paradise Gardens. However, the Telepathic Matrix Project will eliminate all your worries about drone riots, so if drones are the main concern, you're better off holding out for Telepathic Matrix.

If, however, you're closely tied with another faction in the population and diplomacy race for Planetary Governor, Clinical Immortality is much more interesting. Since the value of Planetary Governorship is widely variable, based on your diplomatic status with other factions, it's difficult to pin down a cost-benefit analysis. Assuming you have treaties or pacts with your most prosperous rivals, the trade bonus associated with Planetary Governorship should make up the cost of building this Project in a few turns.

Secret Project animation narrative:
   "And the Lord God said, 'Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live forever, we must send him forth.' Therefore the Lord God sent him forth from the garden of Eden, to till the ground from whence he was taken."
   -- The Conclave Bible,