Our brains are capable of fooling us more than we can admit. I've "noticed" changes after 50 hrs of burn-in - that's quite an effort to run it for 4 days of 12 hrs each (without listening after the initial 2 hrs to get the signature, run tests etc.,). After this effort, the brain expects rewards and hence most times, I've thought that XYZ sounds "better". However, the next day, I realize that the same complaints I had before burn-in have "resurfaced". Some IEMs, which I did burn-in for more than 100 hrs (100 hrs burn-in, 20 hrs of usage) sounded 'better'. But, if I did not use them for a few days and try them again, I've a similar feeling as the first time I heard them out of the box (bass does sound over-powering, sibilance still exists etc., etc.,). For me, burn-in does not work and I'm not about to waste 300 hrs burning in each IEM with noise files to notice some improvement.
Attitude adjustment (accepting the signature as-is, reducing expectations for an IEM to sound the way I want), Slight sacrifices (bass has a longer decay, mids slightly recessed and is only 85% clear compared to some other IEM) work for me all the time. The only two times I hated an IEM out of the box and went on to like them were RE0 (I had zero knowledge about sound at that time), Pana HJE900 (It sounded 'better' after 12 hrs of burn-in, but I also changed tips before trying again, so it could be either). So, if burn-in works for others, it simply does! But for me, it doesn't and I'm not complaining about it.
