I have been using my new VV box mod. I am alternating 2 sets of 14500 Li-ion batteries. The question I have is should I use the batteries until they are completely drained, or do I use them for 3-4 hrs then switch them out for the ones on the charger? I am not sure about what the best way to get the most life out of a set. Any info on this matter would be greatly appreciated!!