My first post to this thread was a quote from Brent Jessee.
I doubt many would dispute his knowledge/claims, as regards vacuum tubes.
Anyone that was interested enough to have checked my previous post would notice: my first reference was to an individual that showed how burn-in affects tubes, on a tube tester (iow: MEASUREMENTS).
The next three, "opinions" were from well recognized equipment manufacturers. I'll simply state that their experience mirrors my own.
Denyin'tologists will never exhaust their reasons to dispute why, whatever the topic might be, won't/can't/shouldn't exist in this universe.
Of course: the vast number of variables extant, as regards systems, room acoustics, source materials, ones listening habits/goals and (PERISH THE THOUGHT) aural acuity, must remain a non-issue in their belief system/doctrine/preaching.