But, Semirhage would have "seen the end of her life approach" if all the Binder does is cut your remaining years (not your allotted lifespan) in half.

Having said that ... 3 oaths have more of an impact than 1 oath, on lifespans. Here's a quote for RJ:

If you committed a violent act, or some sort of criminal act, with a binder, someone who could channel could be constrained from ever doing that again, and the result of having three of the Oaths, is the ageless appearance. One would not produce agelessness, but even one would shorten life, and three of them put a cap on Aes Sedai’s lives, on how long they could live.

So, one oath shortens life - maybe halves? you remaining years, say, while three oaths cap it (at ~300, say, like you suggest). So, one oath wouldn't kill Mesaana, presumably, but maybe 3 would.

It's possible AoLers might develop a Binder that works that way. They may not have even known that 3 oaths would cap a life at a particular age (if that's what 3 do), because they didn't even consider the possibility that they'd have to Bind a channeler more than once.



I don't think one Oath does that, but three Oaths quite possibly may.