When you pull out the cable, pull out using the base of the headphone jack, don't pull on any cables or you'll damage it (regardless of what kind of cable it is). This is the only thing I can think of that'll cause the kink. If you're not using balanced output, there is no reason to unplug the adapter at any point, even for storage, leave it plugged in (I'm sure you don't do this, but just in case).
Keep in mind that all cables do have a natural twist in them, that's why when you wind up the cables using the over-under method.
I'm definitely not pulling on cables at all (ever) so that's not the issue (I have had many earphones before and never had this problem even with the cheaper ones - most of my previous experience was with Etymotics and TF10's).
The issue is that due to having that plug between balanced and unbalance cables being present that particular connection part is heavier than the cables coming out on either side of that connection spot, so that weight pulls everything down and creates weird angles and pulls on both cables (but you are not easily aware of it unless you stick you hand into your pocket - then you can actually feel the cables kinking).