Extremely weak and yet still hinted to be very old (maybe as old as Cadsuane or close).

All we can be sure of is that the stronger a woman, the faster she slows once she starts to channel.

We can't be sure about age, no AS ever said "only the strongest women reach 250 y.o." etc.

It's possible it's connection to the True Source alone that's responsible for mutliplying a person's natural lifespan, whatever that lifespan was to be. An argument for this can be made looking at Morgase, who looks substantilly younger than she's supposed to be and yet barely has the ability, and in fact doesn't channel as until KOD she'd failed to even embrace the Source...

There's probably all sort of other genetic factors coming in, the normal ones. The Aes Sedai of the story die when they reach middle-age. For most people that's when health problems start to develop, and its seems that the ability boost the immune system, making it even less likely AS would have problems in the first half of their lives.

We know from Mesaana that channellers aren't as immune to diseases as AS believe they are, and we know from examples like the extremely old AS in Rhuidean and the toothless wilder of Cadsuane that channellers normally would go through the ailments and problems relative to old age, current WT Aes Sedai just a) never reach that stage of life and b) another effect of the binder is preventing what would be the most visible sign of aging, that is wrinkles. That leaves only the hair as a telling sign - women who've greyed before or by middle-age.