does over under really work?

Yes. I used to do that for all my band's cables. It's called "training" the cable.

But, if your cable's already good and fucked up, it can be difficult.

Hehe, that technique was the first thing we learned on the first day of my high school video production class. Good times. Good times. I'm gonna try and scrounge up my reel now.

It really does work. Without it, the twisting and kinks the cables go through damages them. Maybe that is more important on very expensive cables than headphone cables though.

Shit, sciurus. I took two years of media production in high school and never heard it once. I got screwed.

You learn about methods such as this (I assume, I can't watch the video right now) for climbing rope.

If you coil your rope naively when you put it away, it becomes a twisted mess. If you do a free rappel with such a rope, the twists will all undo themselves, and you may barf on the way down, due to all the spinning. Or you may die from a knot in the rope if your belayer doesn't flake the rope before you climb up.