@mijostin
millercarbon there is a huge difference between mechanical devices and electronic devices. Undoubtedly, electronic equipment drifts slowly overtime as some component values shift with recurrent heat cycles although I have never seen objective evidence of this. There is no electronic device that I know of that changes its characteristics in the first several hours of usage. Imagine what that would do to computers! Certainly tubes need to warm up and stabilize. Maybe class A or highly biased AB amps sound a little different after they heat up although having had several class A amps I have never been able to hear this and again have not seen any objective evidence of this. People come up with a bunch of fuzzy theories why electronics and wires need to break in. All of them conjecture, mythology. I can say that all the full range ESLs I have dealt with do require a period of loosening up. Their diaphragms are tightened up with a heat gun after they are mounted and they do relax over time. This only effects the very low end. Perhaps some dynamic woofers may improve with break in as you can imagine their spiders and surround loosening up a bit with use. But again I have never seen any objective evidence of this.
Thanks for the above. I make tube amps. I cycle and burn them in for 24 hours but only to catch the infant mortalities, which I do. If burnin of electronics was real why wasnt it "discovered" in the 1950's?