Been vaping for about two months and having trouble determining when to replace the atomizers. My local vape store guy keeps telling me I'll taste a definite burnt taste. I havnt yet. Are there any other more objective ways to tell? Does the cotton in the coil look black? Does the juice get darker? I've been using mostly nautilus minis w an iStick 30W. I've changed atomizers twice thinking they were shot, but when I later dissected them the coils and material looked fine