When they are new using them improves their properties as the dielectric forms (insulation between the plates) improving SQ. As a capacitor ages further its leakage increases and capacitance decrease. This has a negative effect on SQ.
The post covered quite a bit, I should have copied the relevant piece out.
Someone put me in a closed little room from which I couldn’t escape, for 24 hours , with Pink Floyd Dark Side of the Moon playing non stop.
I had a burn out.
Burn out isnt a myth.
Either that or those sending items in for a service are deluded.
Probably more to do with your ears than the component.
Same as above.
My first amp, built with Sinclair Project 60 modules, regularly burnt in - and it was incontrovertibly genuine: I could smell the smoke!
(They weren’t tolerant of overload, failure of the output transistors and smouldering of a couple of associated resistors providing effective speaker protection! )
My experience as well. Coming back from holiday, it’s something special.
My theory: Our ears become accustomed to the system (burn -in), so one one hand we know it’s good. We can recognise the strengths and weaknesses. But it also becomes the norm.
Then for a few days we listen to lesser systems and when we return: Wow!
Quite so!You don’t want those pesky engineers trying to bring reality into a hifi forum!
Mark my words. It’ll be Mains cables next.
Doesn’t need to be a theory, it most definitely happens (also given specific examples of this happening to me before on the forums). This is one of the reasons I have a big issue with members that are making comparisons with gear they currently own, to gear they haven’t owned for years & to top it off, listened to lesser gear in between. There is no way you can make any sort of proper comparison.
When I buy a new cable, be it power, Ethernet, or interconnect, I listen first 10 minutes after 1 hour burn in. Then I let the system playing music during 24 hours, without listening to it during that period. ( the night and the day after). Each time, when listening again after 24 hours, I observed a noticeable difference from the very first listening. My brain and my ears couldn’t have been accustomed. For me it’s an evidence.
Agree with you FR…if it sounds better, it is better.
…and…
most of us use our ears to judge if something sounds better, rather than scientific conjecture.
Until quite recently we were free to discuss with our communities our proposed civil engineering projects. People were mostly, yes, yes, you are the engineers, just get on with it. And we got stuff done. Now we have comms teams, and things don’t, well, get done so much.
Sadly the home hifi industry thrives and survives on such things and exploiting customer’s insecurities, I’ve worked all my life very close to the pro audio and production sector and no such things exist in places I’ve experienced - fancy cables, isolation, burn in etc etc, so if it’s good enough to record the music you listen to in the first place it should not be required to listen to it as it was intended afterwards. Most studio environments, if not all that I’ve been in, use boggo mains IEC cables, cheapo off the shelf Ethernet cables and I’ve even seen mains cable used for the main control room monitors in a major internationally recognised recording studio. Just remember there’s a shed load of nonsense and snake oil supporting a multi million £ / € / $ industry.
I’ve read that folk prefer fairy stories to reality.
Indeed, I myself, am very fond of Terry Pratchett (“Lords & Ladies” currently).
Home hifi equipment is not built to the same high standards as pro audio. Obviously.
Bog standard mains leads can be used for pro audio equipment because of the high quality of transformer/smoothing caps used in pro audio make the use of higher quality mains cable unnecessary.
Same goes for ethernet cable.
Apparently some ears need burning in so not a myth after all. 
eh no, another myth
I think this topic is exhausted but what the hell here is my opinion.
People that believe in burn in based on their experience should not suddenly deny their experience.
I don’t believe our aural memory is as poor as people make it out to be. I find it strange how a few people’s objections suddenly has people doubting their own experience.
I completely understand how our ear brain mechanism works and how it becomes accustomed to sound. Equally so I also think if a sound is not right we can identify it.
Burn in is always better because that’s the nature of the process however even after burn in I’m sure many people have still not kept gear they didn’t like.
Most of the time when I’ve burned in a cable, amplifier or speaker I tend not to listen to it. Just let it play in the background. From my initial listen to days or weeks after I have noticed improvements.
I have a problem with my setup at the moment where I cannot recreate the sound I previously had with the same components. Am I crazy? Surely how could I remember what my previous system sounded like 2 years ago? I actually remember it very well. There are passages in songs I’ve heard hundreds of times that don’t sound the same.
My point is trust your ears and if people don’t believe it that’s fine.
(uncontested) Facts of HiFi:
Source first.
DIN sounds better.
Digital sucks.
Speaker cables are directional, note the arrow.
Don’t lock your DINs.
LP12 rules, unless you own a Solstice. 
A 552 takes forever to run-in but it’s worth it.
Don’t use a power conditioner (ever).
Yes, cables do break-in. Get over it.
Everything matters.
In my experience, the most obvious burn-in for me is the Furutech wall outlet which took about 300+ hours before everything sprang to life. The process of the break-in within the first 20 hours was most obvious as it went from good to bad, then to good again and then bad. At that point I was thinking if the outlet will live up to the hype or there’s something wrong with me. Fortunately, the (long) wait was well deserved.
Most of my cables are bought used so I can’t really comment much on that. Equipment and speakers break-in, I can’t recall if I heard a massive change with new gear but it’s there.
Your list is opinion not fact, and disputed on several, maybe many, point!