Off topic, but, burn in does exist....I had the opportunity to A/B a pair of Koss Porta Pro headphones one being my own very well burnt in pair and another being my brothers headphones which had some usage but nowhere near as much as mine - I found there to be a tellable difference between the two - mine felt more refined in every way - but still the difference was not astronomical. If I had to simplify it in visual terms I'd say it was the difference between a kid coloring slightly outside the lines vs a kid coloring within the lines perfectly. No bleedover. Much more honed in.
So then, it's pretty clear to me that burn in does exist as a matter of fact which is irrefutable. The difference it truly makes however ? I'm not one to judge but on my two Koss headphones it wasn't much at all but clearly noticeable all the same.