This is funny; I literally had a dream about what WoT's world without the One Power would be like and I distinctly remember thinking before going to bed that there were no more questions left that would keep me awake at night.

Anyway, I think balefires' only limit is the strength and intentions of the channeler. If the channeler is strong enough to weave an effect that could travel further than the eye could see, the balefire stream would continue onwards even past their visual limit. If the channeler wants to demolish everything in their path, the balefire effect will burn through anything in front of them, but if the channeler is aiming for a specific person or object, the stream might ignore other things to only effect that small space or the discrete item. Rand, for example, is able to weave extremely powerful blasts of balefire, but when he balefired Semirhage, it emerged as a tightly focused beam because she was right in front of him.