Why do cables need break-in?

I just had the experience of having newly introduced speaker cables (AudioQuest AQ-8 bi-wire) break in. When I put them in a few days ago they sounded thin, bright and lacking in bass. Now, after 4 days and 40 - 50 hours, they sound far better: relatively neutral frequency spectrum with much more bass weight. I'm delighted, of course, but I'd like to know why this happens. Will I experience the same scenario when I change interconnects?
When cables are cast the materials form a crystaline structure (which those of us in the audio world refer to as "grain" ).This stucture is relativly random . However,after several hours of use the cable developes a more consistant patern.Thus, creating an easier line of travel for the electrons to follow.
This is not permanent. If you did not use the cable for an extended period, you would have to break them in again.
Why do amps, pre-amps, cd players, speakers, cartridges, and everything else in your system need to be broken-in? The reasons are complex, but the simple answer is that the wire has a crystaline structure that presents many options to the electrons as they negotiate the path one copper molecule to the next. For the first few hours of use the electrons will be seeking the path of least resistance between every molecule. Once that path is discovered, the current flow is much smoother even though the resistance doesn't change. If you take your cables and disconnect them, roll them up and store them, the path will be lost and you'll have to break them in again. Yes, the same holds true for interconnects.
Unless, of course, your electronics generates relatively unintelligent electrons which will never discover, nor remember if they do, the path of least resistance.
Sndsel, how about IQ testing and coaching of unintelligent electrons for the latest tweak? Might be some dough in it , if you market it right.
We might call it ACUE ...Assessment Center for Unintelligent Electrons.
Detlof, LOL! How about TRAINING thus challenged electrons to enhance their skills. Huge market: "Goodbuy expensive cabling, hello expensive (electrons) training!"

Sorry, Pendragn, I'm off subject.

I'm afraid Jack Bybee did that before us, alas !
Q: Why do cables need break-in? A: Because they are BAD.
True, Dekay true, LOL, treat 'em like you would a big bad bronco and ride them real hard ( Put a Kinky Freedman CD on replay for 10 days or so ) apologies Pendragn, still off topic..
My thanks to 2001impala, Sugarbrie, and Audiopath for their explanations and for taking time out to provide them. As for you other guys, try this: My wife and I have a wonderful marriage. It's probably because we go out twice a week. She goes out Tuesday, I go out Friday. (<--courtesy of Henny Youngman):}
Could someone please produce some sources for this? Like, not from people selling cables.
How about, "Hooked on 'electron'ics".
Not a single scientific explanation here...I'd like one, please!
I suppose, you are very well aware of the fact, that there is no really convincing scientific explanation for this.
Our ears tell us though, that this phenomenon exists. So if you " believe " in science, you'll say that the ears are wrong and if you believe in what you are hearing, you'll say that science falls short of the fact and cannot explain it. P l e a se lets not start this argument again, because it leads nowhere!
There has to be. It's called MSE, or materials science engineering. Some things have no scientific explanation (that's why I'm Psychicanimal--I saw in a dream the girl I'm in love with the day before flying to her country and met her two days later...wow!) but something like this in the 21st century must have one.

To start, science is not a belief. I am a professional scientist. I do not 'believe' in science. Scientific activities search for truth through a systematic process. That's why it starts with observation (or hearing, in this case). Questions arise, hypotheses are formulated and experiments to sustain or defeat those hypotheses are conducted. An inseparable part of this is a process called validation (Quality Control/Quality Asessment).

Does anyone have any validated data sets/explanations?

I do not wish to create controversy. I bought some silver plated copper speaker wire very cheap and two people I really trust told me there would be a long break in perion for the silver. That the sound would get better. How can this be?
Here's my two cents coupled with a little cable geometry theory. I think it has less to do with the wire and more to do with the insulation. In my experience cables with more di-electric material and higher native electrical impedience generally need more break in time. Pure silver definately sounds different than copper or plated silver but all else being equal it's the cable geometry that determines the break in period and how the cable settles in to your system.

Teflon foam or air tube and teflon dielectric combinations seem to take less time to break in and the less gap between conductors the faster the break in too. It seems to be a matter of the capacitance of the cable as related to AC impedience in the audio spectrum. A small charge builds up in the dielectric. If the cable has a low impedience (like Goertz or Nordost for example) it tends to have a very short break in period. If on the other hand it has a dielectric foam insulation and a relatively higher impedance and gap between conductors then the break in is longer. To my ears Audioquest type cables and others like them seem to have longer break in periods. The end results seem close in sound but cables with polystrene and nitrate foams seem to take 50 to 100 hours before they sound almost as good as a Nordost or Goertz out of the box. This is just my opinion and a little information gleaned from listening and reading specs. I hope that it is somewhat helpful.
I agree it is the dielectric. Capacitors also need break in. Once I replaced my power supply capacitors in my amp. The sound was very bright and thin. After 100 hours everything was back to normal. The dielctric needed to be "formed up," I believe this is true of cables.
Psych, it's not the silver, but the quality of the insulation, as explained by Dmi....
Can somebody help to get power capacitors for my Jadis DEFY 7 ???
The dielectric is what break's in more so than the conductor's.The dielectric takes some time to break-into it's optimal electrical properties.That's why you can have have two identical cables with different dielectric's sound totally different.Audioquest uses batteries to keep their dielectric's constantly at peak performance,not the conductor's.
It's the DIELECTRIC inside a cable which needs break in.