I can't remember if I posted this here or elsewhere, I hang out in several forums.
I think that the devices and delivery methods make a big difference, having moved from cigalikes all the way to pulsed vw and either vivi novas, rebuildable drippers and genesis style atties.
In the UK if you want something between 6 mg and zero you have to make it yourself or dilute, there's nothing between 0 mg and 6 mg. Here it goes, in ready-made juice, 0,6, 12, 18, 24, plus a few sold at 36 and two (I think) at 45 mg/ml.
The highest base nicotine that is legal to buy in the UK without a poisons license is 75 mg/ml, but nobody would vape that! Intellicig (bought at the end of last year by BAT) have been running clinical trials in hope of getting an MA (which would be needed for over 2 mg in 0.5 ml if the EU draft Tobacco Control Directive passes as is) and they have proved it is safe to vape 45 mg/ml, that's the highest they sell. Here Flavourart sell 45mg/ml as well, and a few use it, some only when they know they have to go a long time without
vaping as most seem to vape a lot less at that strength.
I was close to a chain-smoker, one every 15 minutes, sometimes less. At 18 mg or less I'm a chain vaper so I use two strengths, 24 mg/ml in tnhe morning, especially when I first get up, and 18 mg/ml later in the day. It seems that once I've topped up with the higher nic, I can drop to 18 mg without chain
vaping.
I have a feeling that it would be hard to find out how many puffs anybody takes in any single period for the simple fact that people don't count. Studies have been based on cigarettes, 10 puffs in 15 minutes, but vaping doesn't work like that, there is no beginning or end, a pv doesn't stop working after 15 minute or an hour (unless it's a tiny cigalike with a tiny cart, very small cigalikes can have a 1 hour battery life). So I put 3 ml in and that lasts me all day, or most of it. My battery lasts a little over a day.
That means I can say how much I get through in a 24 hour period, but I'm not vaping for 24 hours. Sometimes I could be vaping for 20 minutes, other times not at all for an hour, and you have to subtract sleep plus times when vaping doesn't work well (a vamo while driving is awkward) or not allowed.
I think that poll-based studies should be based on how many mls used in 24 hours, plus strength. I suspect that the lower the strength the higher the intake, which would even out to equivalent to the number of cigarettes that used to be smoked.
Also I think it should be remembered that there are different types of vapers. Some use it as a form of NRT with the aim of cutting nicotine to zero, some vape as healthier and cheaper than smoking and have no plan to cut down or stop, plus a large number (maybe the silent majority who aren't on forums) are dual fuel, they vape either to reduce the number of cigarettes smoked or in places where smoking is banned.
I was in that group, all I wanted to do was save money and improve health by cutting down on the cigarettes smoked, but when I bought high-performance gear I found I was missing out on the cigarettes without noticing it. As long as I have a pack I'm happy not to light one, but if I have none I want to smoke. I discovered that recently when I decided to get rid of my last pack as I wasn't smoking them. I became obsessed with smoking and bought more within a few hours, actually smoked six of them until I was back to normal.
I don't know if that's my personal weird psychological quirk or if others feel the need to possess a few cigarettes 'just in case', that owning them gives the freedom not to smoke them. I also don't know if that peculiarity is caused by the decades of anti-smoking propaganda as I've always been an instictive rebel against being told what I can and cannot do if it harms nobody else.