I also believe it’s the duration of use and not the concentration of use that plays more a role here. Being a heavy smoker for 4 years isn’t the same
mentally as someone who smoked normally for 20 years. I think past the 10 year mark and your brain has suffered damage to the point where the addiction becomes life. However, in about 10% of cases, smokers who quit were able to because the effects of nicotine addiction hadn’t taken hold. Much like some people feel nothing from taking cocaine.
IANAE though.
Either way. I was a smoker but not a heroin user and quitting was the hardest thing for me. It took me almost a month to feel normal.