NO ONE KNOWS!! :DDD The rules are made up and change in every continuity and frequently also within continuity. Sometimes they're only tens of thousands of years old, but often they go up to several million and I think in the latest continuity even the "youngest" cast members are Literally Billions of years old.
My personal read is that aging is a combination of entropy and obsolescence. Like, if you can afford it and want to keep getting upgraded, you can just keep on going. Their consciousness are essentially post-singularity AI, which are capable of learning and self-improving, so in that way they work just like humans, staying "themselves" despite turning into someone totally different through a sense of continuity with themselves.
So a lot of the characters who are canonically "old" are that way essentially just because they haven't bothered or haven't been able to keep staying young. No upgrades, only repairs; no massive system-wide rebuilds, no massive overhauls to match the system specs of the modal average across the planet. Stay stubborn enough about wanting to be who you are, and eventually you'll systems will have "aged out" and become one of those folks who shake their helms at newbuilds and go "they don't make'em like they used to".
Of course upgrading and rebuilding takes its own stress on the software running on it, which also "ages" it. Driver and hardware mismatches, software running without "parent" libraries because those were replaced in an upgrade but the reference wasn't, bad addresses and a lot of other minor programming problems that can self-repair (or be repaired by a specialist), but which is often less noticeable than, say, suddenly realising your interfacing equipment is incompatible with someone. "Maturity" in a species born "adult" like they are comes from the living code repairing those kind of problems and slowly becoming more internally referential and robust -- which then goes on to contribute to the "aging" whenever some bigger injury/upgrade comes along :'D
I haven't really gotten as far as thinking about how this affects characters post-canon (other than that My Favourite is prolly gonna have chronic pain because that's how I roll) but I hope I at least gave a plausible answer to the second question!
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My personal read is that aging is a combination of entropy and obsolescence. Like, if you can afford it and want to keep getting upgraded, you can just keep on going. Their consciousness are essentially post-singularity AI, which are capable of learning and self-improving, so in that way they work just like humans, staying "themselves" despite turning into someone totally different through a sense of continuity with themselves.
So a lot of the characters who are canonically "old" are that way essentially just because they haven't bothered or haven't been able to keep staying young. No upgrades, only repairs; no massive system-wide rebuilds, no massive overhauls to match the system specs of the modal average across the planet. Stay stubborn enough about wanting to be who you are, and eventually you'll systems will have "aged out" and become one of those folks who shake their helms at newbuilds and go "they don't make'em like they used to".
Of course upgrading and rebuilding takes its own stress on the software running on it, which also "ages" it. Driver and hardware mismatches, software running without "parent" libraries because those were replaced in an upgrade but the reference wasn't, bad addresses and a lot of other minor programming problems that can self-repair (or be repaired by a specialist), but which is often less noticeable than, say, suddenly realising your interfacing equipment is incompatible with someone. "Maturity" in a species born "adult" like they are comes from the living code repairing those kind of problems and slowly becoming more internally referential and robust -- which then goes on to contribute to the "aging" whenever some bigger injury/upgrade comes along :'D
I haven't really gotten as far as thinking about how this affects characters post-canon (other than that My Favourite is prolly gonna have chronic pain because that's how I roll) but I hope I at least gave a plausible answer to the second question!