How does the sound change as power cables burn in?

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.