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
Ditto, Megasam, I have done that very thing, and there was a major difference between two of the same power cords.
I kind of performed this test but with the same pair of cables. When I purchased my used HT IC's (already broken in) I knew about directionality but did not know which way the arrows were supposed to go. First time round I had then backwards. It only took about 20 seconds to figure out that something was wrong. I switched them immediatley and they sounded a lot better.
If a tree falls over in a forest and no one is there did it make a noise?
I am a music teacher-making my living by giving pipils reports on their changing sound-based on my aural memory. Changes caused by burn-in are slow but amazing. Raanan