There has been very little spotlight on Nomios, which according to the in-game description is lead by a "...ruling bureaucracy, a secretive fragment of the Mbaye-Gogol directorate which claims to have survived since the Collapse - in mind rather than body, if the rumors are true." This is no argument against Kanta's lifespan, haphazard as it may be, being a unique case. It rather reinforces the concept that some extremely wealthy individuals may in fact have access to technology, exceptionally skilled surgeons or simply an abundant source of spare organs in the form of the Cryosanctum. After all, if the M-G leadership somehow survived, we are talking about multiple beings older than 200 years.
The "in mind rather than body" part raises a few questions regarding the longevity of the Mbaye-Gogol execs. From the Story missions we know of the possibility of cloning, which would be a rather simple explanation. The "how" of it may be a bit more interesting. Is consciousness transference somehow being used? Are the clones taking over the roles after their predecessors die? (Thinking of the Weyouns from DS9 here.) Or would this be something more akin to transferring the minds of people into machinery, computers or possibly sentient AI cores?
Regarding Artemisia Sun, we only know for sure that she has been active as of cycle 189, orchestrating the 2nd AI War as CEO. Presumably she was active for a long time before that, rising to the CEO's office would most likely have taken a significant amount of time. However with the scarcity of news about her we cannot rule out the possibility of her being a persona made by an AI core. Obviously this is nowhere stated so it's just a conspiracy theory on my part, but as AI cores are acknowledged to be able to create multiple very plausible personalities, I think it's entirely feasible that some elements of Tri-Tach are just AI cores (or maybe just a single AI core) in disguise. As we know nothing about the possible deterioration of AI cores due to the passing of time (we know of them getting bricked in P-space), the Artemisia/Tri-Tach-construct may be hundreds of years old.
There's no real information on what the standard life-expectancy is in the sector, though some characters could have supplemental text added to help pinpoint this (thinking on Adonya Coureuse, or Archcurate Jaspis).