@douglas_schroeder
Hmmm, I can only comment from admittedly limited experience. I have upgraded from a well run-in Antelope Audio Zodiac Gold to a Zodiac Platinum. For the first 500(!) hours I thought I had made a mistake until literally all of a sudden the fog cleared and I had substantially enhanced micro-detail, soundstage width and depth as well as significantly improved impulse performance.
In a similar vain, I replaced JAN Philips 7581a tubes with NOS cryo‘ed Svetlana Winged-C 6L6GCs in my Wavac EC 300b amp.
The goal was to eliminate a slightly forward, discant emphasising sound. What I got for the first 50 hours was numb, incongruous sound and I was ready to give up. All of a sudden though, holographic soundstage, sweet but intense violin sound and an overall organic presentation that I was looking for.
In summary: while I agree that for basic ‘good-better’ comparisons, burn-in can be largely ignored, for real fine tuning it is essential to account for it.