Unfortunately it is not that easy. Of course there are companies who tell you to burn in so that your brain gets used to it.
But on the other hand, it makes sense for several other things. Sometimes it is measurable, then it is easy, but sometimes it is not, and then the discussion starts.
What I always like is, when someone can convince me with some physics, why it makes sense or not.
What I did with my FDX was: Testing them A-B with another another IEM, and of course, with the same measured loudness within 0.2 dB. Then burned in for 50 hours without listening, and repeating the test with the same tracks and volume. Then it was very easy to hear the difference of the burn in process. Of course it is still subjective and just my opinion, but that is what I can do at home with my equipment. I haven't started that process with the Xelentos, that is why I asked.