so although BAs aren't supposed to need burning in, I found that the W4s really benefitted after about 60 or so hours of play time on them, along with some intense pink, white, and frequency sweeps sessions, in the end the treble came around on them, I was really quiet surprised, but in the end end! lol, the ASGs won over the bass head in me? hhmmm go figure,
After I received one of the first W4 to ship I posted that they were the first balanced armature IEM that I've tried which opened up and became more spacious and detailed with over 24 hours of burn-in. It's strange, because I listened to them for 30 minutes and then I set them aside for 24 hours with loud music playing, and then listened again for the 1st time in 24 hours - and the change was pretty apparent in terms of how much more open and crisp they were (and thus more immersive or enjoyable). There was no way I "got used to their sound" when I wasn't even listening during that time. I have not heard this with other BA IEMs since.
I feel like I've had the W4 forever, and they are still the one audiophile universal IEM that I carry around with me everywhere, along with an inexpensive iPhone microphone headset (like NE-600M or V-Moda Vibrato). I own the Triple.fi 10 Pro vi with microphone and they sit unused in a box under my bed, after I had to glue them back together because they didn't hold up in my pocket after 2 weeks. The W4 have traveled thousands of miles with me and still look new. I kept meaning to try the TF10Pro vi mic cable with the UM3X-R but never got around to it. I'll have to do that with some W4R instead.
Changing the subject - like Spyro says, the W4 are an elegant and non-fatiguing IEM for general all around use. I have half a dozen high-end custom IEM, and when I'm at home I use those most with a well matched DAC and amp, so fatigue isn't an issue for me like it is with him. But because I don't want to risk losing an $800-$1200 custom when I'm mobile I'm carrying around the W4.
When I went to Mexico for Christmas last year I only took the W4 with me, not because they're better than my customs but because they are safer and more convenient - and I agree that I'm not losing a whole lot in comparison (sound-wise). The W4 are clearly better than my Livewires customs or Freq-Show, my SE-530 re-shelled into customs, or my Alien Ears C3 customs (which replaced the Freq-Show but were so bright and harsh that I GAVE THEM AWAY). I do think if I could only pick one universal fit IEM to own, it would be the W4, although the rest of my high-end customs are better than (UE11Pro, ES3X, ES5, JH13Pro x2, JH16 Freq-Phase). But sound alone doesn't drive the choice of what I carry around or use in certain circumstances. It's picking the right tool for the particular job. Note - I almost didn't put the UE11Pro in the list of "better" due to their mid-bass bloom, but when they are used with my Woo WA6 or ZDT desktop amps they really shine.