Most will tell you its nonsense. It seems clear that break in for woofer fundamental
resonance is not required. For high power, it does make sense to gradually increase power
so certain epoxies and glues stabilize. Ferro Fluid contained drivers would seem to have
the least chance of having anything to do with break in. The ferro fluid also makes
it resonant frequency so a lot less relavant. If you think you should, do it.

I think on high powered drivers, the voice coil impedance can double on power peaks
owing to 3 dB power compression. Its got to be getting pretty hot to do that.

greg