Hi Senna74,
Yes the milleniums do take a while to break in. I've experienced this with a pair of the Linbrook monitors and now also with my Ref IIIs (I ordered the millenium tweeter to replace the standard revelator). After they're finally broken in, they sound excellent with no sibilance, excellent snap and decay characteristics, and gobs of soundstaging. You're getting close though - 200 hours is close to what I put on my Linbrooks before they finally blossomed.
