Breaking in a sub works! I played my subs at low volume, everday for 2 hours, for 2 weeks before I turned it up. 1 week is probably enough for most people.
Each day I would do a bench mark with my eyes closed, when the car was running, how responsive my subs were becoming.
By the 2 week break in, my subs were much louder and very responsive to the lower end of the spectrum.
Still, I kept it mild for a while after that, just to ensure I wouldn't break anything once I REALLY cranked it up! After dialing everything in, ANY type of music sounds amazing through my setup. From chest thumping kick drums to eye rattling bass, I can play my system with authority!