I'd say you're just vaping more because there's no effect on your system from the nicotine, whether it's a throat hit, or just the consumption of the drug telling you to slow down. I know when I vape 0mg I chain-vape more and will deplete my 1ml clearos in a rather short period of time, but loading the same thing with my usual 24 or 36mg blends of the same flavor they'll last me five or six times as long.