This is a list of F&SF books I could think of on the theme of life extension.
Binder, Eando: Anton York, Immortal: elixir that revs up radiogenic receivers in cells.
Blish, James: cities in flight series: anti-agathic (anti-death) drugs.
Bunch & Cole: Sten series: eternal emperor with backup bodies receiving current data.
Butler, Octavia: patternist series: vampiric spirit take-over of new bodies.
Clarke, Arthur C.: “Death and the Senator”: secret program.
Dalmas, John: Yngling series: psionic takeover/transfer.
Duncan, Dave: Strings: organages growing clones for rich/powerful/ruthless.
Haldeman, Joe: The Long Habit of Living (Buying Time): expensive treatments.
Heinlein, Robert A.: future history: Howard Families (humans bred for longevity) & extensive research into transfusions, transplants & cloned parts.
High, Philip E.: Reality Forbidden: medical treatments from Supreme + same results from dream machine.
Kenyon, Sherrilyn: Dark Hunter series: Dark Hunters lifespan bestowed by goddess, Apollites stealing souls, were creatures from magical melding.
Laumer, Keith: A Trace of Memory: race that regenerates but needs offline memory.
McIntosh, J. T.: Flight from Rebirth: treatments turn old into new teen without memories.
Niven, Larry: A World Out of Time: special teleport booth that teleports accumulated junk out of cells.
Niven, Larry: known space series: organ bank period; artificial living organs; boosterspice longevity drug.
Pierce, John R.: “Invariant”: short story, perfect repair treatment also stops brain changes.
Rackham, John: Time to Live: transfer soul & memory to young body.
Smith, Edward E.: Masters of Space: replace carbon with silicon & fluorine (plus other modifications to eat radiation).
Spinrad, Norman: Bug Jack Barron: organs harvested from the poor.
Turtledove, Harry: Noninterference: unintentional effect of medicine.
Van Vogt, A. E.: Null-A series: backup bodies passively receiving from active.
Vinge, Vernor: True Names: copy memories to network.
Wagner, Karl Edward: Kane series: curse?
Watt-Evans, Lawrence: With a Single Spell: unintentional effect of magic spell.
Weber, David: Mutineer’s Moon trilogy: augmentation with biotechnics.
Weber, David: Honor Harrington series: deliberate mutations, “prolong” treatment.
Weber, David: The Apocalypse Troll: Methuselah symbiote.
Wilson, F. Paul: Healer: body invaded by psionic symbiont/symbiote.
Zelazny, Roger: This Immortal: mutation?