It's not so much that the wire has to be identified along the entire length; rather, it's the (often ignored) requirement that the neutral be marked at every junction, splice, and pull point. Ever try to guess exactly which 3" of wire will end up in the LB?
"Painting" is used by the NEC as a verb ... and not as a noun. Thus, while it brings to mind an image of someone sitting there with a little jar of paint and a small brush, the term is also an accurate description of what you do when you run over the insulation with a marking pen.
I think we're going to wind up changing our practices, and making shrink tube our 'default' marking method. Why? Because the newer, slicker wire simply doesn't hold tape well. We may even have to resort to finding a way to remove the outer nylon cover.
