Likewise, I haven't noticed earth-shaking differences after cleaning. I've used both the alcohol and running water methods. Some atomizers seemed to work better after cleaning (but not much better). I drowned one in the water. Another tasted of rubbing alcohol for days. Bottom line: I rarely resort to cleaning them, but do stand them on end periodically to drain the crud out.
It seems to me that a death blow for atomizers is letting liquid evaporate overnight and leave solids of crud on the atomizer. That crud comes from particulates in the liquid. Remember that whatever you find on your atomizer is duplicated inside your lungs. I think the quality of
e-liquid is underestimated in its influence on both our atomizers and the long-term consequences of e-smoking. And what do we really know?
My own plan involves fine lab filtering of liquids before I use them for vapor. Course, I'm working with a lot of homebrew stuff, but I plan to filter E-Ciggies liquids that I still have. The fewer particulates the better -- for me and the atomizers.