18650? Damn the only problem with 2 of those in a PV is the size. I could also use a motorcycle battery but again the size. In the long run your going to find with 2 sets of batteries you can vape forever. Also in the long run when you figure all the PVs you buy in the constant upgrading in the end the Infinity or Buzz covers them all. Then you won't end up like us with a stack of PVs and Mods we have that now collect dust since we got our Infinities because it does what each one of the others do all by itself. I have 16340 mods, 14400 mods, 14500 mods, 18650 mods, and adjustable voltage passthrough that can be powered by anything from 2x 3.7volt batteries to 30 volt and is now on a 12 power supply that's ac fed but none of them are as good as my Infinity or my Buzz because that's what I'm vaping on. Another good thing is if you set it at 3.95 volts every puff you take will be at that level until the battery needs a charge. None of that declining voltage as the battery loses power. Then put that set in the charger and your other set in the Infinity and continue on. There is no time restriction.
Another thing, why use LRs that are not needed and drive your batteries harder when you don't need to? They were made to compete with HV vaping.
Wharf has the answer.