Power cord - 5 ft vs 10 ft ?

It's not the length so much as the girth that's important.

Most of my power cords are of the DIY persuasion and I have a nice stash of Oyaide 046 and 004 plugs.  I bought a few hundred feet of rather good silver plated solid core copper wire some years ago and have built several power cords of varying lengths, from just a couple feet to a few meters.  I've used these on all my components over the years and yes, I have experimented to see if a short cord sounded different than a long with the same wire and plugs and I really couldn't discern a difference of any significance.  There might have been the slightest of differences but, in my systems and to my ear, it was truly negligible.

I put things comically, but I think gauge is important. Not all important, but important. There's a lot of information out there. My approach has been to try to spend enough so I was not using a cheap cord, but not so much that the cost started to be too high in proportion to my system.

I have heard demonstrations with power cables costing $2k and $7k and I could hear a difference -- in that system, that room. That didn't make me touch my wallet, however, because I want to change the weakest links, first, and I have a ways to go.

This video was interesting: 

I have heard 4 feet, but have never heard a difference in terms of length, so I just get a cord that gets me to the outlet on the power conditioner.

@hilde45 everything matters and the plugs make a significant difference. I have experimented with using different connectors on several power cords including stock cable and there’s definitely an improvement.