Do speaker cables need a burn in period?

Musician, Physician, EE degree, Ham, Audiophile. No, cables do not have burn in or have directionality. Many things CAN change such as your listening position, air density and your ears and brain. But for those who do believe in wires with magic properties, it is harmless fun. Unless they talk you out of real money. And you get to decide what that is.
This is my thought based on experience physics and physiology. Because the OP asked. Could I be wrong? Of course. And I will be equally surprised if the rapture happens or Atlantis rises. But you never know.
If your experience suggest things that violate well established scientific norms I would usually suggest to any student to ponder, hard, alternative explanations, other than "oh all that estblished science is wrong".  But IF you really have the chops and the data to PROVE that old science wrong, I assure you the Nobel committee is listening. Nobody on this forum has done so, so you mignt look elsewhere for facts on wire and signal transmisson.
Because the OP asked. Many lovely people believe otherwise.

Thing is Geoff, nobody HAS given you a Nobel prize. The "appeal to authority" is not MY authority but say, about a million lbs of EE and Physics texts back to Maxwell and Faraday and hundreds of universities, thousand of recording studios and all those players of Strads who laugh at your directional or burnt in wire. Yeah. Appeal to those authorities.

I undestand very well science is incomplete and open to progression and change. But the physics of electron flow and signal transmission is extremely well established as to basic principals.  These princilals are well measurable by incredibly sophisticated techniques. We also undertand the limits of the human ear. What IS open to much more understanding and theorizing is the human mind and its perceptions of speech and music. As well as its ability to form tribal alliances and belief systems. That is why I think it is probabilistically much more likely that tne explanations for perceptions we are discussing are found there. By many orders of magnitude. These are not perfect arguments, none are, but highly likely ones.
Some good reading is by Jonathan Haight, Daniel Levetin, Leonid Perlovsky (who has some fascinating ideas on the "purpose" of music and how it might in turn influence perception).
I am trying to advance the principals by which open minded people can parse challenging ideas with many parts, which does include some appeal to authority IF that authority is well grounded. Otherwise we are just living in our own heads. I have no interest in a pissing contest with GK, rather I am making a case for interested parties, like the OP, from the perspective of someone who has looked into many of the overlapping areas in some depth. BTW my personal starting point of thinking about the issues was that different wire would improve my audio listening experience.

Addendum for Andy2. I respectfully suggest the billiard anology is incomplete for electron flow. Quantum principals come into play, the role of "electron drift" vs signal transmission makes for fascinating reading. For me, the bottom line is that for signal in vs signal out, in the wires we are discussing, the physics is well established and not altered by a few hundred hours of music olaying time.

Hifiman
No, at least I, me, this EE, do not believe we have science derived explanations for many things in the universe, and especially in our heads. But for audio frequency signal transmission over several meters of cable, yes, I do.
Don't forget that the military and big industry has had huge interest and investment in this exact topic for over 100 years.  So they have looked hard at both hypothesis and practicality.

Yes I think "manufacturers lie or are just plain wrong".  The why is debatable of course but will seem obvious to many.
GK, no, I do not think "anyone who disagrees with me js engaging in a pissing contest". Just you.
For the others, just stating how and why I arrived at my understanding. No animus intended.  A few people might find some ideas to ponder.  As I pondered the "just listen" arguments and did my best to apply them. Probably enough said by me on this topic. Enjoy and share the music, by whatever means makea you happy.

I for one am not calling anyone a moron, just suggesting we inhabit completely different paradigms concerning what science is or isn't.

" You may want to wait for a 6'5" black belt, amateur boxer to finish his sentence before telling him he is a moron. :

That wasn't a veiled threat was it?

no2headphones:
Challenging  issues you raise. Not everyone here is an industry shill, some are just true believers without much respect for concepts like double blind, established physics, expectation bias etc. They are fine people but no point in arguing religion.
To have real discussions with science/engineering oriented music lovers who want to discuss audio, including the possibilities of edgy stuff/ limits of audibility, tinkering etc etc would likely need to be established on another forum since Audiogon is about selling stuff. And the "magic"  cable properties are a big part of the "stuff" that is sold in the whole market.

No2headphones:
Well I am probably not the best one to asked about site conduct since I was just emailed that some of my posts will be deleted  by a moderator.
I get it. Go away ganainm ! No science here! OK I'm gone. We can both poke around for alternatives. DIY Audio does have some folks who know one end of a soldering iron from another but have not been in a while. Good luck....