for those that rebuild, dry burning and re-wicking is the best way to maintain quality of vape. Coils themselves will last months, but need to cleaned occasionally and re-wicked, for optimal performance.
Changeable atty's, are for those that don't know how to build, or choose not to. Dry burning is done without the wick in place, and cleans the gunk buildup on the coils, then re-wick.