I also do 3ml to 4ml of juice a day at 12mg of nico. I used to smoke a pack a day of marlboro's as well. I find that if your bored or have a little free time here and there, im just puffing away on my pv, which isnt bad because thats what I used to do with my analogs anyways. I just try to relieve my nico cravings all day, and its working for me right now at 12mg. Just because someone tells you to smoke in the higher nico mg's, like 18mg, while that might work for your cravings, you might not like how strong it is. For me at 18mg, it worked for cravings, but depending on who makes the juice, was too harsh for my throat. So just keep doing what your doing if it works. To me, you know your overdoing it if you feel that sickness overload of nicotine in your system lol...
I have this question in mind for long time, " if u've vaped for a long time, one year maybe, what's the thing that keeps u vaping "? very curious.
If you're only vaping 8mg/ml then that's like an ultra light cigarette. Marlborough lights aren't that light. A better fit might be 12 - 18 mg/ml liquid.
Having said that, 2 tanks is maybe 5 - 6 ml per day which isn't that bad. You will find that as time goes by you will need to vape less, unless you're just picking it up to have something to do with your hands. Stay with it and don't worry too much unless you start to have real problems, like cravings.
I'm six months tobacco free and have gone from 10ml of 18mg/ml per day (ex rollie smoker) to about 4ml of 10mg/ml per day. Looking at the totals, that is going from 180 mg per day down to 40 mg per day, and I now very easily get a nicotine overdose even though I've recently dropped to 10 mg/ml from 12 mg/ml. I might have to drop it to 8 mg/ml myself very soon.
Everyone is different and you will change with time. Don't worry about the quantity you are vaping so much - you are not smoking.