Break in means that the response drifts over time. Any cone material or surround material that is unstable over time, in a manner enough to effect audible sound, is probably not such a great choice of material for a speaker.
If it drifts after several 100 hours of play.....what will the sound be like after several thousand or tens of thousands of hours played. In all likelihood, at some point, the speaker will have drifted away from its intended or factory calibrated response.
Cars used to require a careful drive in period and not because they were great cars; it was a manufacturing quality problem and tolerances were poor and surfaces had a higher wear during break in. Eventually this has been solved with higher quality manufacturing techniques.
If it drifts after several 100 hours of play.....what will the sound be like after several thousand or tens of thousands of hours played. In all likelihood, at some point, the speaker will have drifted away from its intended or factory calibrated response.
Cars used to require a careful drive in period and not because they were great cars; it was a manufacturing quality problem and tolerances were poor and surfaces had a higher wear during break in. Eventually this has been solved with higher quality manufacturing techniques.