...EDIT: Wish I could go flavorless... probably could go eons on a wick
I only do flavorless with my DIY, and in TC mode, I've gone more than 2 weeks before changing cotton on an RDA. Even so, when looking at that 2-week old cotton, and it is vaped nearly dry, it is almost pure white like when first installed.
With the BB, I am testing different builds across all the different atomizer choices that I am pulling out the build way before I notice any burnt or dry hits.
With the VapeShell, you can almost vape the tank dry, and then you get the slight cotton tasting hit, which then the next hit is a slight dry/burnt hit if using Kanthal, but if using SS in TC mode, there is just little-to-no vapor output, similar to when you get the flashing battery icon on the screen...
But even so, if 17w on a 1.0 Ohm Kanthal build, a dry hit is not anywhere as harsh as it might be on a 0.25 Ohm RDA @ 35w, which usually triggers a mild coughing fit for me.