and god hope he doesn't quit vaping cause cigarettes won't do anything anymore to him .. maybe 5 packs per day.
it's not a big plus, i don't want to crave for cigarettes when my battery dies out in the middle of holiday or even when i don't have the posibility to vape and need to buy a pack so my body's nicotine level matches vaping nicotine level.. i'd say 1-2mg per ml and vaping like 10ml per day of some creamy custard or fruits would do the deal.You have to remember though that even if someone vapes more nicotine, they are vaping zero tar and other toxins.
I have to agree with what @oldhippydude says, when i quit after 47 years i couldn't of coped without Nic Salts but the longer i have vaped the less nicotine i use, i am now on 12mg which is still high according to some vapers but i was smoking along time and Nicotine has become a bit of a crutch to keep me on the straight and narrow road to not needing it anymore, but for now 12mg is good and i can't honestly remember how good my health has been during my lifetime, i feel great atm.