To answer the poster, the time it takes for burning is the time that you believe. If you expect great results in a minute you will hear them. If you expect them in an hour you will hear them. If you feel it will take ten days it will take 10 days. These types of devices and accessories that proliferate do so because of expectations: the power of suggestion and the placebo effect.
Are there differences in cables? Absolutely. Are there differences due to break in? How could there be? The signal is an AC signal....that means no "direction of flow", electrons buzz back and forth in their orbits around the nuclei, with no net positive charge, no net negative charge. So no "forming" of dielectric is possible.
Expectations. Filtering them out, keeping them from affecting comparisons, can be very difficult.