Let's not let this go too far off the rails. Break-in is real, completely repeatable and obvious unless you do not possess good listening skills or a sufficiently resolving system. I have broken in dozens of components, and cables over the last fifty years.
One of the more interesting experiences was that I was able to break in three Audio Research Reference 160 amps. Each of which I had for over 1,000 hours. To my amazement the sequence was exactly the same on each case. Starting trebly and a bit flat and improving through about 120 hours, then wavering wildly between sounding terrible and great... before resuming a slow improvement through 600 hours.
A unique characteristic of the Audio Research Reference 5SE after breaking was that after each turn on / starting to play music from cold there would be a very notable jump in fidelity at about fifteen minutes... but if you turned it on without playing music... you still had to play music through it for fifteen minutes before the improvement occurred. I thought it was interesting. Then I saw someone on a forum bring up the very same characteristic. And another owner jumped in and confirmed. The Audio Research 6 / SE does not do this. It sounds great from startup there is no jump in fidelity... other than a very small one.
I could relate stories about dozens of components and wires that I have broken in over the years. So, let's not get too carried away that it doesn't exist or it's in your head. I've been comparing notes with people with good listening skills and systems for decades and never met with anyone who could not hear it on most good equipment. The degree and details does vary by component. Many components are run long and hard before sale. But there is still typically a break in period. I just recently received a fully broking in amp that sounded terrible for the first day...then was fine again.
