Burn-in time Vs. Getting used to a sound


I have had much in the way of high end audio over the years. ...and the idea of an electronic item needing several hundred hours of use before sounding their best..is an accepted idea now (for the most part). Recently I have heard a growing thought of this just being the user getting used to the sound of a product.. Truthfully in the early days of Large Advents, DQ-10 Dahlquists and other gear..there was never any talk of burn-in time... Any thoughts out there on this.... Truth or Hype?
whatjd
Thanks to all for your thoughts. I feel that burn/break-in is real for the most part..and have heard it in audio gear. ...and, of course, felt it in baseball gloves..and sports cars. At the same time I know that I can want something to be some way...that I have to watch myself so that I don't think it into being that way....rather than it actually being so. Kind of like the tests where people are given sugar pills and, thinking they are taking a medication, re-act accordingly.
If burn-in exists, how come the cables don't continue to burn-in continuously and perpetually and instead apparently reach a sort of "stable" state ? That just doesn't make sense to me, perhaps someone can explain.
Joe: Why does it take a few minutes, at least, to bring a pot of water to a boil? Does water ever really go away, even when the Hydrogen is released in extreme reactions, or does it just complete a cycle and come back as water again?
Joe_coherent that is a good question and I don't know the answer. But I know burn-in is for real. I have suffered thru it. It is very easy to find out for yourself. Compare a broke-in pair of ICs to a new pair.