As my Europa literature says (2003 edition), they will not break in with quiet playing. I discovered this to be true as I played them at modest listening levels with no significant change.
Break in calls for 200 hours at "moderately loud levels (30 watts)." To me, that's LOUD.
I know that Roy does not hesitate to really crank it as I personally discovered at his factory. We had it up to 106 dB, A weighted, at 2 metres (my measurement). He didn't flinch. The speakers didn't distort. Stunning.
So, according to my interpretation, and considering "30 watts" (a lot), "moderately" might mean: keep it below 95 dB. In other words, LOUD, just not insanely loud. If you want to discuss it with Roy, give him a call.
My experience with Europa's:
1) Since I had established an expectation from my factory experience, my Europa's out of the box sounded bad in comparison--gritty, edgy, "overly analytical."
3) With 200 hours of loud playing, they are dramatically improved, and I am very happy with them. Their coloration is nicely balanced, portraying the level of warmth as found in the recording--in short, neutral.
4) To trace back over their break-in history, I noticed perceptible changes at these loud playing intervals (counting only the really loud playing hours): at very roughly 2-3 hrs., 10 hrs., 30, 60-80, and then around 200-ish. The change from beginning to end was incredible. Only time will tell if they have finally stabilized for the truly long-run.
Low level detail is really remarkable. They play loud very well, too.
To answer your question about further break-in, Tcbannon, I suspect that you will find further change for the better. Keep 'em cranked when you can. That's what makes the difference.