Hmmm, there are clearly 2 schools of thought.
1. Mr. Feil, with over 50 years of audiophilic experience on hundreds of components, a respected Esoteric dealer with broad Esoteric brand experience in his own regard, and a proud owner of C-03 himself, assures us with well founded authority that at the 200 hours mark, the device has reached peak performance.
2. JBM and I, eternally skeptical of any hopes of an even moderately quick gratification, prefer to err on the side of a perhaps over conservative caution, and recommend a long break in of 600 to 1200 hours. I in particular, being a notorious and unabashed fan of Esoteric products, although I regret that I do not own a C-03 preamplifier, suspect that the unit will still open up considerably for several hundred hours to come.
Who is right or wrong is of course of little importance.
Rather, I suggest that you continue the break in of the utterly unbrakable, and let us know if the sound evolves further, or if it has now already reached its performance limit at 200 hours.
Saluti e buone cose,