Can You Expalin Why Power Cables Do This?

It has to do with handling and connecting a power cable that's been "broken in" before but has been laying around out of use, and what happens once you reconnect the power cable and it "settles in." (It can be a power cord on an amplifier or cd player, etc.)

Why, when you first plug in many power cables in the situation above, do they start out adding more bass weight and clarity to the presentation (often, not always). Then the power cable goes through a (stabilization, "settling in") or whatever you call it. With this stabilizing or settling in, the original bass and weight dissipates. The original clarity dissipates. Within a day or two (or 3) after "settling in," when you listen to the system, the presentation has changed. Now the presentation has lost some of that clarity and bass weight from before (I guess audiophiles call this a "tightening" of the bass, and the dissipation of clarity is called what? (the highs getting smoother?)

What's happening? Any EE's out there with a not too technical explanation in laymen's terms that average folks can relate to about this "re-settling?" I wish "broken in" power cables, continued adding the good attributes to the system before and after "settling in." (you know, bass weight, clarity etc.) I'd like to keep those sonic qualities not lose them. What's happening?
Thanks