I don't want to stir a discussion that's OT, but burn-in is simply psychological IMO. It's just pseudoscience, people draw conclusions of changes in sound based on their poor sonic memories without having a proper reference to go by. When the science has actually been done, it points to insignificant change. This is why also see a lot of people claiming BAs and MAs go through burn-in, but that's also false as well IMO (and it's funny how some attribute it to cable or crossover burn-in without any grounds).
Have I experience change? yes, it's actually very relative to the IEMs you are using at the time. Using the EX600s for a while, it made the DDM's sound veiled and recessed in the treble. Then a month later after using other warmer IEMs, going back to the DDM2s it seemed to have opened up, but I wouldn't call that burn-in and leave it at that, it's just not logical IMO. Manufacturers benefit from claiming their product requires a significant amount of burn-in knowing the psychological changes.
Bah, the formatting in this review got pretty screwed up somehow...I'll try to fix it soon.
