It's pretty clear from the start of the Wheel of Time that Jordan hadn't figured out how long everybody lived yet. Aes Sedai could clearly live a long time, but it seems like he'd thought of it on the order of "about a century" rather than "up to 300 years". Picking Siuan as Amyrlin at 40 is insane if she's going to hold the job for 200+ years, but makes more sense if she might keep it for 60.
It also makes the Age of Legends unusually fucked up. If the "Servants of All" could live upwards of 600 years! and the common folk only got to a normal healthy long-life (good medical care, etc) of around 100 or so. They become this multi-generation ruling magical class, and no amounts of discipline would keep that from becoming a fantastically massive political issue.
However, we also have (a) the metaphor of the Expulsion from Eden to draw from, where they "ate of the tree of knowledge" and introduced death into the world and (b) knowledge that ter'angreal allowed normal people to use certain weaves on a regular basis. So if you have:
It isn't use of the One Power, but presence of it flowing through a body that prevents (and reverses aging)
A large number of standing flows throughout the cities
Really good magical healing
and you could imagine that non-channelers could also have extremely long lives of multiple centuries. Further, the disparity would be much reduced between channelers of different abilities, too, if everybody was exposed to the same level of background One Power. Only the very strongest channelers might live longer, and maybe not by a whole lot.
But I can do one better. We already have a thing called the Tree of Life that gives feelings of peace and contentment, that lined all the streets of cities in the Age of Legends.
What if Avendesora/Chora trees have the effect they do by releasing a standing flow of the One Power that provides the minor healing / de-aging effect of the one power, for everyone?
