Lazarus Long And Hugh Valland

If a lot of people lived indefinitely extended lifespans, then younger immortals would have to find ways to recognize and respect older immortals, at least some of whom would have become maturer and wiser over their centuries or millennia.

When Robert Heinlein's Howard Families - not immortal but long-lived - meet, Mary Sperling declares her age, one hundred and eight-three, and, when no one present claims to be older, chairs the meeting because she is the Senior. When Lazarus Long, challenged about his identity, discloses that his birth name was Woodrow Wilson Smith, he is asked in astonishment how old he is and, when he owns up to being two hundred and thirteen, he must replace Sperling in the chair. His style is far less formal than hers but is accepted because he is the Senior. He will turn out be a mutant immortal that need not have been born among the Howards who have been merely selected for longevity.

In Poul Anderson's World Without Stars, when Felipe Argens meets Hugh Valland, the latter:

"...thrust out a muscular hand. Archaic for certain!" (II, p. 10)

When Valland declares his name, Argens is startled because:

"...I'm old enough to recognize that anyone bearing a name like that must be a great deal older.'" (p. 11)

Indeed, Valland is the Lazarus Long of his timeline. Heinlein made a mess of writing further volumes about Long but Anderson would have done a good job if he had continued the biography of Valland. 

To ship under Captain Argens, Valland must be a gunner who can double as a second deck officer and ideally must also have some xenological skill. Valland is old enough to have learned from experience before anyone had started to teach such skills:

"'I think I can claim the whole lot,' he answered. 'No formal trainin'. By the time they got around to foundin' academies in such subjects, I'd already been in space for quite a spell.'" (p. 12)

What an asset Valland would be as an academy student. He would know how to learn whatever there was to be learned from an academy course and would also know how to pass on his accumulated knowledge without patronising or denigrating anyone else. A true Senior. He would be asked to stay and teach but probably would not want to.

Would immortals just keep working in the same line of work indefinitely? I think that people would find different ways to use all that time like long periods of what would call "retirement" followed maybe by complete changes of career direction. In Larry Niven's Known Space future history, as I recall, one character had spent a normal working lifetime on Earth. Thanks to suspended animation, he was able to emigrate to an extra-solar colony. Thanks to boosterspice, the Known Space equivalent of anti-agathics or the antithanatic, he would then live through a second working lifetime in a different profession. What a life experience.