Well, I have no amp break-in experience other than my monoblocks. Other than my initial impression of stronger, tighter bass from the M80's, (which I did not expect) there was no further improvement over time that I could perceive.
I also have had recent experience with entry-level audiophile headphones (or is that 'audiopile'?) ... and many people over at head-fi tout break-in times of 50-200 hours depending on the cans and who you pay attention to, as well as cable upgrades (pls let's not get into that!). I gave it a shot for the heck of it, cause I still like to consider myself open-minded on the subject, and after about 70 hours... I hear no difference. Excellent cans, no diff. (Audio-Technica A900's) Oh, and I wouldn't offer my PB-13, even in jest.
