Yeah just so nobody spend too much for parts - this compares Premium, Vapor4Life and LiteCigUSA (the basic colors) parts
http://www.e-cigarette-forum.com/forum/new-members-forum/104464-v4l-vapor-king-premium-pr110.html
Also - if you have auto batteries and damage or kill one with a juice leak, consider the KR808D-1 manuals which are not dependent on a drag sensor right inside the hole in the threaded end of the battery. Manuals also won't turn on accidentally from wind or vibration.
Re cartos - if you ran a carto dry all the way to a singed taste, that taste won't go away
If you top off a carto as you vape (whenever it needs a bit, to keep it damp) then it can take a while for the flavor to change over totally and by then the performance of the carto may be degraded. I recommend you try to top off with flavors you don't mind mixed. Like Peach into a tobacco would make a nice Peach Tobacco, Cherry into vanilla makes a cherry vanilla, etc.