personally I'm trying to find the smallest possible battery to last me all day. I vape around 6ml a day and so far I tried a 1,000 mah pack and it's more than enough for me, I ran the 6ml bottle from completely filled with only a tiny air bubble till dry as a bone with power to spare, only problem is it makes the mod pretty fat as a bottom feeder, but power wise that's better than any 18650's ever been, from vtc4's &5's to 25r's and whatever, no comparison, the 1,000 mah 3s pack beats them all hands down.
the 1,000 pack is very fat at 18mm+ so I tried going thinner and went with 3 single 600mah cells and was able to squeeze one in between the bottle and the chip in a T cell layout. now the whole mod is nice and small and very comfortable to use and easily pocketable, but with only the 3 600 cells it can't make it the full 6ml, it died at about 4ml from the first charge. I think it might get a little better after a few cycles, might make it closer to 5ml. right now even with only 600mah 3s it's getting as much life as a typical 1,800-2,000 mah 18650 would, so it's really not that bad, but I might have to give it a few 15min usb boosts during the day to make it run through the full 6ml
it might be worth it for me for a tiny mod. only way to squeeze more battery in is to make it bigger and I don't really want to

gonna try to live with it and see, it's almost as small as the reference mod and it's got a 6ml bottle in there too
everybody's got different needs, if someone needs 4-6 18650's a day how much juice are they going thorough? sounds like ~16-24ml a day there... wow, I rarely go much more than 6 ml a day, 20 ml's a day is a lot of juice