In Poul Anderson's World Without Stars, the antithantic has ended aging and death by old age for all mankind. Many people trade and explore between galaxies. A spaceship can make an instantaneous jump to any other galaxy when it has accelerated to equalise velocities. Memories are periodically edited to prevent insanity through memory overload and people have learned patience.
In James Blish's Cities In Flight, the anti-agathics have ended aging and death by old age for the small minority who fly cities between stars faster than light. Immortals do not overload with memories because they leave the remembering of facts to computers. However, they have learned to see solutions to problems almost instantly and are impatient with those who don't.