How does the sound change as power cables burn in?

What are the key changes you have experienced? Which cable? In which characteristic? How long does it take? How big was the change? etc
Almost any cables have a bit of stridency when first put on. over time that lessens.
The issue of cable burn-in and how many hours s required has been discussed here repeatedly. There is absolutely no way to know for sure what any amount of time may change for a cable unless you can do a direct comparison to another same exact cable that has not yet been used. And then many people would argue that you have "disturbed" the cable in the system such that such a comparison is then invalid.

I have done many rapid power cord swaps back and forth between different models (both with many hours on them) and the sonic signature of each is immediately apparent. And thus the point raised in the last sentence of the previous paragraph does not stand for me.
rapid power cord swaps...How rapid is rapid? This is an important point. That you the listener with or without a 2nd party can only be so rapid swapping PC in and out and yet still retain Musical memory is questionable.
Rapid as in listen to 2-3 tracks and then jump to cord2 do the same, and then return to cord1. In a highly resolving system, significant differences can be heard between many pairs of power cords. Examples include NBS Statement vs. Kubala Sosna Emotion, Purist Dominus Ferox vs. Kubala Sosna Emotion, Stealth M5000 vs. Stealth Dream, Dream State Dream Catcher vs. Stealth Dream,

If this is questionable, that is your problem, not mine.
Initially a new cable will sound dull/flat, then it will get bright/strident for a number of hours as it opens up. Finally things with smooth out.

Regardless, you can pretty much tell the sonic signature of significantly different cables right out of the package.
All horse crap when thinking you hear a difference from new to burnt in.

Having the same cable, one with no hrs. And one with 10 billion hrs and I did an A/B Without the listener knowing what cable was what he would not be able to pick out the new cable @ 80% of the time.

If you can you get a free Charlie Brown CD.

Most of this hobby is head games and I have played them many times with wire.
Oh. Here we go again.......
Cable threads are better than free admission to an amusement park.

And there's no long lines with smelly people standing alongside you.
depends on how long it takes for your ears to acclimate to the sounds of different components or different cables...your ears will ajust to the new sounds over time...
Whenever I have gotten a new power cord I just put it on a piece of equipment that will pass current through it for 240 hours or so and then install it in my system and listen. The sound of my system with the power cable in place is what it is.

I know I have no baseline to compare what the cord sounded like before and after burn-in but my reasoning for doing this is that pretty much every burn in thread I've come across has stated aftermarket cables change/improve the SQ of your component after 200 hours or so of break in. To me why go through the trouble of the swapping back and forth and wondering. Just run the cable in and listen.
Some cables, usually excellent ones, continue improving after 200 hours but not dramatically. And not only power cords.
I would have to agree with Glory. I can understand an interconnect having an effect on sound but not a power cord. I am all for having a good quality power cord so it can deliver the proper amount of current but because it is before the power supply I just can't see how burn-in has any effect at all on a power cord.
Can you understand how a Bumblebee flies? It's an aerodynamic impossiblility. There are quite a few things that work in this world, that no one actually has a concrete answer for, YET! One thing I DO know; Any improvements to the power supply of a piece of audio gear(and/or the power to it), can provide great sonic benefit.
Liguy, you completely missed the point made by Glory. Glory did not dismiss that power cords can have an affect on sound. The point was that there was no difference from a cord right off the production line to how it will sound after it has been burned in.

Good point Rodman99999
there is no consistent pattern to the change in sound of a cable as it "ages". having auditioned and reviewed many products, i can attetst to noticing veiling and attenuation of the highs, initially, with some, and as has benn mentioned, an unbalanced frequency response, favoring the treble, in others.

break-in does not always improve the sound. in some cases the true character emerges, e.g., brightness, which is not apparent at first.