I just ran another 30' of #10 wire down the frame of my truck to power an air-compressor.
As I was threading the wire along-side of several more of various gauges, serving various purposes, it just came to me-----a brainstorm!!
If, when I first got my truck, I had ran a 2, or 4, gauge cable, from the front to the rear, splicing in an isolated terminal stud at strategic points along the way, I could have used shorter, more efficient, runs of the smaller wires, simply by tapping power from the nearest HOT stud.
As it is, I have always ran a wire of sufficient size to easily carry the load being added; but, usually, the gauge of wire is plenty big enough for the job it's doing, but not big enough to tap into and add another load.
I may as well run the big cable, and add the HOT access studs along the way; else, I will roll and tumble nights, doing it over and over in my head.
Anyway, copper is like dirt-cheap, and I have worlds of time on my hands.