I can't believe in the burn-in process. One can understand burn-in for speakers (especially for low frequency sound). With time, the continuous movement of the paper cone, will make the paper less stiff. But the resistance of a metal cannot change (and that too for the better) just by running it with electricity representing an audio wave. If such a thing happens, why doesn't burn-in process cause deterioration? Is there some kind of God that ensures that, since we have spent tons on money on audio equipment, sound should improve by running it for few days? Also is the devil keeping silent on this issue of audio burn-in?
Cables are not automobile engine which has moving parts and neither cables is wine where slow chemical reaction keep on changing the taste of the wine with years of storage.
Some folks try to explain that it is the capacitance (or inductance) that causes this to happen and it takes time for charge, etc to build up. The capacitance of such cables will be in micro farads or milli farads and it will just take a microsecond to charge it up.
If something cannot be explained by physics along with an equation which gives you the burn-in time as a function of the current, voltage, wave frequency, etc, then any explanation of burn-in for cables, etc is some kind of snake oil.