I would say, break-in of audio gear is often more a parroted urban legend than a reality.
It is often suggested the capacitors need warming up time to "settle" and "form".
Well, I don't know about all these "special capacitors that sound so warm", I often held my ear close to 'em and never caught a peep...(grin)
If a coupling capacitor measures 1 µF right from the start as it should I wonder what other parameters would need to be settled in?
Inductance? Measure it and you'll find a value so small it can't possibly influence the sound...
Fellow Gunslingers et al, beware, there's a lot of snake oil specialists around!
Don't want to offend any real believers though!