I started with V2 before they introduced their "4.2V" battery. As it is not regulated, performance degrades. An 808 size batt usually has a capacity of 280mAh on the outside (for the non-shorty variety).
I can drain one with 2.6-2.8 cartos in 3-4 hours (not chain
vaping, but fairly regular).
This is anecdotal only: Based on the taste-flavor from my VV at 4.2V (regulated), the drop off on one of these 808 batts from full charge is within the first 30mins of use. Decent enough for the size, but continues downhill until depleted 3-4hrs later.
The price point they offer these batteries at is too high (IMHO) vs comparable 808 batts at other vendors. They all work about the same, I'd rather go by price and get more sticks for the same $$$.