Trope-a-Day: You Can’t Go Home Again

You Cant Go Home Again: A consequence of lighthugger travel and the ensuing time dilation for ephemerals; or people from ephemeral societies, rather, since its the high cultural delta of the society you left that causes the problem.

Also, more rarely, what happens to people left off-world at the time of an Apocalypse How or Gone Horribly Right.

Trope-a-Day: Longevity Treatment / Immortality Inducer

Longevity Treatment / Immortality Inducer: Immortagens, which are Exactly What It Says On The Tin, along with mind-state backups. (Previously anagathics, too, but technology marches on, etc., and why settle for a few extra centuries when you can aim for eternity?)

The Empire, or groups within it rather, works hard on selling these to absolutely everyone, on the entirely reasonable grounds that anyone who wants to die and/or doesn’t want to not die is obviously nuts, and anyone who advocates for death in general is even crazier than that. (See also: Immortality Immorality.)