@Ryokan: That's why I said it's very unlikely that your experience is due to burn-in. I've measured it on quite a few IEMs over the years and the outcome has always been the same: very slight and insignificant changes overall, the biggest ones during the very first minutes of use, steadily decreasing and pretty much settled after one hour at max.
I've remeasured several IEMs after months of use, and, on the condition of consistent tips and placement in the coupler, never observed any further changes.
From my pov, it's much more likely that something else has changed, provided it's not just a change in your perception. If you use small bore tips, they may cut down on treble and make IEMs sound less thin and aggressive. Foam tips may bend and obscure part of the nozzle, to a similar effect. A small amount of earwax may accumulate over time on the protecting mesh or in some internal filter. Your ears could have accumulated more wax inside. Heck, your hearing may even have undergone objective changes over the course of one year. Do you have it checked regularly? Last not least, and considering we're talking about opulent 10-BAs-per-side IEMs, one driver might have just stopped working without you noticing anything but them sounding a little more agreeable. Half joking, but in all seriousness, even that would imo be a more likely explanation than "burn-in".
