Do cables need to be re-broken in?

People with lousy (nonexistent) listening skills love to crack jokes. The differences some of these things make are beyond easy to hear. One time I came home to a new IC and with little time between shifts raced to hook it up right out of the box. It was a used cable, should have been broken in, sounded absolutely horrible. Not imperfect, not disappointing, not bad. Horrible. Awful. Bad enough I lost sleep that night wondering what might have gone wrong. 

The next day at work it dawned on me, I didn't recall checking direction. That night first thing sure enough it was backwards. Switched around and warmed up it still needed a few hours to settle in but now it sounded really good.

These things do happen. They do make a difference. Just not a difference everyone is able to hear. That much at least is clear.

Of course. Only its minutes not months, and movement matters more so than time. In other words your system warms up every night, and all the wire not having signal running through it is a part of that warm up. That's with nothing being moved around. Moving a cable around, all the bending and flexing, it will be a few to several minutes settling in after that. Try it and see.