I can go pretty much all day on a set of 18350's in my VVG. Like JC Okie, I just carry an extra set just in case. I have a couple DNA20 mods and having the fancy little readout is kind of cool, but the VVG is just as easy if not easier to use. I try and build the same coil for my rba's on my VVG's and it's simply a matter of dialing up or down a smidge here or there. Once I'm dialed in, I don't have to worry about it anymore just get to squonking. Looking at the internals for a DNA20, there's a lot of stuff that goes in there and I would think that Robert would have to make his casing a fair amount larger to accomodate everything. 