Prof - I understand your skepticism about burn-in. All I can tell you is that I've heard it's effects by testing identical interconnects after one set spent 48 hrs. on a cable-cooker. There were 5 or 6 people there. We all clearly hard the difference and could identify the 'cooked' cable. And only one of us knew which cable was which.
We did that test specifically due to skepticism (like yours) that maybe you just "get used" to components & cables, rather than any real burn-in.
But Prof, speakers?? You've got to be kidding. They're essentially motors with moving parts, and there WILL be physical break-in, always.
If you know a dealer, this is an easy blind test too. Have him set up two pair of the same spkrs - his broken-in demos and a pair straight out of the box. I'll be very surprised if they sound the same to you.
Now, I'll agree with you that for most applications, wires do not need break-in. They conduct electricity very well 'out of the box'. But there's something different (more!) going on when they're used in audio.
We're probably (IMHO 'clearly') dealing with things that a heart monitor or a computer don't 'care' about.
At least that is what I've heard many times over many years.