I don't worry about it, and I chain vape like a demon. I did have to lower my mg down to 12 though, because the 18 was getting to be too much. I look at it this way - I smoked 2 or more packs a day. If I have to have my PV glued to my mouth all dang day long to make me a happy non-smoker, then I'm perfectly ok with that. Days when I'm really busy I vape less, days with lots of down time, computer time, etc, I am pretty much vaping nonstop. So? I can tell if I'm getting too much, because I FEEL IT. Then I'll voluntarily put it down for awhile, or as I said, vape a lower nic. I really don't think I am going to vape myself sick more than once, because my body won't let me, I start feeling awful. It's no different than being physically unable to smoke an entire carton of cigarettes in 2 hours. Yeah, you maybe could, but you wouldn't. Or if you did, you'd not do it twice!