I get a weird sense of satisfaction when I can vape my clearos nearly dry. If there's a little bit of juice moving around in the bottom I feel cheated. Generally only my Protanks let me do that, my T3s don't cooperate as much. I suspect it's the well in the bottom of the Protank, it probably just looks empty when there's a few drops left.
With as hot as it's been this summer, however, I tend to get more gurgles and leaking if I don't refill when there's less than 1/4 of a tank left, and I use all VG. For outdoor festivals I'm thinking I will need to make some juice that I don't dilute at all so I'm not a leaky, sticky mess when it's over 100 degrees outside.