When I put in the Wheelhouse 150s we were house shopping so I was living in an extended stay hotel. I had to play at below bedroom volumes for 10-months and the speakers sounded great. When I joined the band the speakers got pushed with the Marshall for a few months when I had trouble with my 4x12 and shined. Not sure if they are "broken in" but they sound better and better at all volumes. I have the cab back at the house now with the JC again and it is simply a monster.
Think about how polar opposite a Marshall JCM200 and a Roland JC120 are, the speakers sound phenomenal with both amps.