What does occur instead is, user burn-in. I've noticed it myself with speakers I bought that were well used, and over 15 years old. The more I listened to them, the more I liked them. Same with amps.
What I know as "burn-in," is when something becomes predictably reliable to the point where it's apparent that it will likely make it well past it's warranty coverage after not blowing up the first few weeks. In other words, it has survived multiple on-off, hot-cold cycles with no cooking/burning smell.
User burn in, what a good concept. As you know, I'm having speakers built by Jim Salk. In an interview for a magazine the writer asked him about burn in time on his speakers. His answer was point blank blunt : there is no such thing. After listening to 1,000's of hours of speaker testing, good speakers sound the same after 5 minutes of play as 500 hours of play. Burn in in Jim Salks opinion, and his opinion is as valid as any EE's, is a myth for speakers.
Speakers are the most likely item to need a "burn in" in a sound system since they are electro-mechanical devices that move and have points of friction and wear. If Mr Salk says "nope", then I can support that.
User burn in, or the user getting adjusted to the sound system, is a concept I can fully support. I've said it before, the user is the least reliable part of a sound system. Golden ears or no, users of sound systems probably need the adjustment period far more than an electrical component. Once again MrBoat you have illustrated a great concept not in the textbooks of them young whippernsappers.