Relative output of your driver's did not change more than a fraction of a db after the first few hours. The crossover points may have changed a very small amount.Back in the day, we broke in studio woofers with a Crown DC-300 input pad plugged into the wall. Played 60Hz for at least 24 hours before swapping. Never measured for any level difference, but sonically, un-buzzed woofers sounded flat and lifeless. Old woofers were sent back for reconing. Mid/Tweet drivers could be reconed on site. Techs used to hang shredded diaphragms on the wall marked with the band / musician who blew them.
Note that the above speakers were abused and suffered mechanical failure.
To the long break-in crowd:
Do you log listening room parameters Temperature, Pressure, Humidity, Line Voltage? see ieLogical WinterBlues
How accurate is your level control? [Have you ever verified it?]
Have you verified the amp is operating at EXACTLY the same BIAS point?
My 35 year old speakers break-in CONTINOUSLY due to the above. The CBLF is infallible and contributes not...