I've never before noticed any effects of "break-in," and it doesn't seem plausible to me that any sort of prolonged "break-in" would somehow tend to improve (rather than degrade) performance. So, I wasn't terribly optimistic that the low-end extension of my pair of Dayton HF 15s (for home system) would improve over time. However, LFE really did seem to improve during the first couple/few months. It certainly could be all in my head though.

In any case, I am very happy with my HF 15s (in 3 cubes sealed ea.) ...though I can't help wondering how much more I'd like them ported.