2/4 #5
Do you rebuild your heads? I have several boxes of spare heads that I haven't used because I rebuild the coils in the heads I do use. Even if you aren't into rebuilding the coils themselves, you can still prolong the use of your heads by replacing the wick after dry-burning and cleaning the coil (if you're interested in this, let me know and I'll PM you some instructions). This saves the expense of having to continually buy new replacement heads and can even improve their flavor and/or longevity. The Kanger heads are easy to fix--I'm not sure about the Aspire heads.
One of the problems you may be experiencing with the Kanger coils (based on the tanks you cited), is the fact that the heads are dual coil. This sometimes improves the flavor (arguable), but it also presents multiple points of failure versus a single point with a single coil. And, because the two coils are stacked on one another, the top coil usually burns out faster than the bottom one. With these sorts of heads, I like to rebuild them with a single, larger coil.
Just some thoughts.... I know that it can sound intimidating, but re-wicking is incredibly easy. Coil building is a little more complicated, but not all that much harder.
(Since this is my last contest post for the day, I'll post any replies on the other thread.)