I'm not recommending it, but I'm testing army surplus telephone wire for my dynohub setup. 23awg 2 conductor zip line with 4 tinned copper strands and 3 galvanized steel strands per conductor. The insulation is very tough as well, I'm able to split it and run a conductor down the rolled seam of my Honjo fenders. I've also installed it in a Peugeot, replacing the original internal downtube wire. it used the frame as chassis ground, I'm running twin conductor, for an independent ground.

On one bike I've looped it loosely once around the head tube-fork crown area. On the other I've turned the wire around a rod to make a coiled section from the hole in the down tube to the fork mounted light. I think they will both last a long time.