I have heard some changes on other phones, but definitely not to the same extent as what I have experienced on the SQ5. I was familiar with with the sound of an AKG K701 which the shop had for auditioning. However, when my friend bought his pair, the high end was not quite the same. There were some resonances on his pair which did not exist on the shop's pair when he let me try it after he just bought it. However, after a week (of his own usage) some of the harshness was gone, but I found that it was still not quite what I was expecting it to be.
After subsequent weeks, I did feel his K701 sound was changing, but past the first week, the subtle changes I heard could very well be just be the "mood" of my ears or psychological. The only significant period of change I would really swear I heard was only during the first week.
However, with my current pair of IEMs i use on the go (Hippo Shroom). I found there was no significant change in the sound from when it was new up till now, and when it was new, it sounded to me to be the same as the pair I had auditioned at the shop.
My take is perhaps manufacturing tolerances resulting in each piece of audio equipment would not be exactly the same causes the burn in effect to be more significant in some than others. Perhaps as inherent characteristics of each design could cause it to be more or less prone to this burn-in effect?
Definitely I have not heard any kind of sound change that is even close to what I experienced with the SQ5. I also wonder how such behavior is possible with a total absence of bass on week 0, changing to (what i consider to be) too much bass on week 1.