Well, these headphones are said to have a crazy break-in time.
I'm not sure if it's our ears getting used to the sound signature of certain/new speakers or headphones after some time or if the actual piece of equipment goes through changes and "breaks in." Both hypotheses make sense to me. Perhaps, both?
Vacuum tubes, however, definitely do break in and come into their own. Then decline.
you know what's great about Fleetwood Mac ... those guys/girls were clearly masochists. sleeping with eachother, cheating on eachother while in the same band ... then writing songs about it and singing it to eachother ... tell me that ain't metal