Wayne,
How is the durability and longevity of the product affected by how high above the ground that it is installed? By the way, I have never been paid to install NM cable as a permanent part of a building. I use conduit and wire, but I don't see any increase in hazard when the NM is installed at a higher elevation. No one could prove that there is any increase in hazard and that is why the NFPA Standards Council was forced to permit it in these building under the threat of major a lawsuit. The code cannot be used to support certain products or require the use of additional labor units unless there is proof that these installation methods are required for "the practical safeguarding of persons and property from hazards arising from the use of electricity".
As far as knob and tube, if you exclude the fact that it doesn't have an EGC it is among the safest wiring methods ever used in a building when it has not been modified by DIYers.
Don(resqcapt19)
