Weaves don't have "edges". The weave creates an effect; the effect simulates a sharp edge. - Edit 1
Before modification by RugbyPlayingAshaman at 03/01/2011 10:52:20 PM
For example the wards erected around Callandor were tied off, inverted and made to last forever, until the right person came and undid them. There is no indication that any of them lost effectiveness over time. As RJ said, a weave that is tied off could last forever - it is up to the intentions of the channeler to determine whether tying one off is appropriate or not.
A weave isn't a physical construct; the flows form an energy matrix, and this matrix produces an effect, but it is in no way bound by the rules of the physical world. This is part of the reason why Aes Sedai are considered so much more powerful than a blademaster despite the fact that the Tower had not participated in large scale battles in centuries. A single Sister, not even among the strongest, could weave a barrier that could hold out any number of enemies indefinitely. You can't "beat down" a weave creating a wall of air - you'd need another channeler to neutralize it.
A weave isn't a physical construct; the flows form an energy matrix, and this matrix produces an effect, but it is in no way bound by the rules of the physical world. This is part of the reason why Aes Sedai are considered so much more powerful than a blademaster despite the fact that the Tower had not participated in large scale battles in centuries. A single Sister, not even among the strongest, could weave a barrier that could hold out any number of enemies indefinitely. You can't "beat down" a weave creating a wall of air - you'd need another channeler to neutralize it.