Isn't that the truth but then they seem to not be aware of (or choose to ignore) scientific measurements from Douglas Self which shows the burn-in of polyester capacitors (something Cyril Bateman had already studied & measured some time before). An article published in Linear Audio "Douglas Self - Self-improvement for capacitors" can be found in which he shows measurements that show a reduction in non-linearity over the short term & over long term & furthermore shows that a certain percentage of the improvement in non-linearity is retained 90 days later & a build up of further reductions in non-linearities are found & mostly retained with usage.
To quote Doug Self on these matters, is to quote Surgeon General in defense of cigarette companies
. Have you read his book on amplifier design? The preface to the book is nothing but railing against audiophile concepts such as we are talking about. He goes point by point damning any such claims. Here is the bit on capacitors:
"Capacitors affect the signal passing through them in a way invisible to distortion measurements.
Several writers have praised the technique of subtracting pulse signals passed through two different sorts of capacitor, claiming that the non-zero residue proves that capacitors can introduce audible errors. My view is that these tests expose only well-known capacitor shortcomings such as dielectric absorption and series resistance, plus perhaps the vulnerability of the dielectric film in electrolytics to reverse-biasing. No one has yet shown how these relate to capacitor audibility in properly designed equipment."
Self, Douglas; Self, Douglas. Audio Power Amplifier Design Handbook (Kindle Locations 956-959). Taylor and Francis. Kindle Edition.
So you think a guy with this kind of view about capacitors, would support burn-in in them resulting in audible differences? I don't think so.
Right after that, he talks about cables:
"Concern over cables is widespread, but it can be said with confidence that there is as yet not a shred of evidence to support it. Any piece of wire passes a sine wave with unmeasurable distortion, and so simple notions of inter-crystal rectification or ‘micro-diodes’ can be discounted, quite apart from the fact that such behaviour is absolutely ruled out by established materials science. No plausible means of detecting, let alone measuring, cable degradation has ever been proposed."
Self, Douglas; Self, Douglas. Audio Power Amplifier Design Handbook (Kindle Locations 962-966). Taylor and Francis. Kindle Edition.
He has the harshest words for the entire concept of subjectivity:
"Articles of Faith: The Tenets of Subjectivism
All of the alleged effects listed below have received considerable affirmation in the audio press, to the point where some are treated as facts.
The reality is that none of them has in the last 15 years proved susceptible to objective confirmation. This sad record is perhaps equalled only by students of parapsychology."
Self, Douglas; Self, Douglas. Audio Power Amplifier Design Handbook (Kindle Locations 940-943). Taylor and Francis. Kindle Edition.
Back to you using his tests of polyester caps to justify burn-in, no need for that because Doug does the same in pages you can't view online:
"Finally, have I stumbled on an effect that explains why some people insist on the need to burn-in so-called high-end hifi for days before it sounds right? Could it be that lurking
in that high-end equipment there might be some polyester capacitors that need straightening out? Well, let’s see.
The effect only applies to capacitors acting to define time-constants, so it would be restricted to RIAA equalisation networks, tone-controls if you have them, and just possibly sub-sonic filters. It would also only work if the ‘burn-in’ was accomplished by having signals of 9 Vrms or so continuously present in the circuitry. Unless your preamplifier has a very funny gain structure indeed, this is not going to happen, though you could put some extra amplification between the cartridge and the preamplifier input. You would also need to change the vinyl continuously to keep the signal coming in. That is not, as far as I know, what even the most devoted audiophiles do.
Looks like the hypothesis is untenable. A lot of questions remain unanswered. Will a 10 kHz test signal linearise capacitors ten times as fast? Would exercising the capacitors with a sawtooth waveform be equally effective? Presumably it would-it’s not as if the capacitor is being taught what a sine-wave looks like.
However, given the availability of polypropylene capacitors that never distort at all, it’s questionable how much time should be devoted to this interesting effect.
Self, Douglas. Self on Audio: The Collected Audio Design Articles of Douglas Self (pp. 171-172). Taylor and Francis. Kindle Edition.
So as you see John, he doesn't make a good witness for this topic.