I too was alittle skeppy on speaker breakin
until I heard it for myself when I brought home my new PSB Image T45s. The bass was very weak for the 1st 24 hours or so but the more I played them, the stronger the bass got. I don't mean loose and sloppy ..just stronger and more apparent..
But that being said, I to would be very skeptical of dealers touting speaker breakin as an excuse for poor sounding speakers. If I were a dealer, I'd make dam sure that all my demo's were broken in before putting them out on the floor. Sounds like this guy is trying to make a fast buck..