hmmm, I typically only use my Prodigy which I can run at either 5 volts or 6. I can use either 801 penstyle attys or 510s or 901s on it and have found that my attys actually have been lasting longer, it maybe that the higher voltage is producing just enough heat to keep the gunk burned off. Not sure why.
I hardly ever have any burned or melted filler, but I always keep mine topped off and never wait till it is dry to do so. My favorite is my 510 attys on the prodigy as the vapor seems dryer, more like real smoke, but I use the penstyle while on the road for the bigger cart so I don't have to refill as often. The vapor producation is huge compared to standard voltage.