I would think, after such heavy usage, stopping would be next to impossible. I didn’t use these drugs but smoked tobacco and that was hell to quit. Makes you wonder doesn’t it.
Larry Sinclair doesn’t seem to ‘wonder’, he appears to know!
He hasn't done that either.
Nicotine is actually one of the most physically addictive drugs. It is only acceptable because it doesn’t cause profound mood altering effects or impairment (as long as the addict can keep smoking). Even so, it permanently alters brain chemistry just like ‘hard’ drugs.
Some people are so addicted that they smoke constantly and go through incredible pain if they try to stop. They smoke from the moment they wake up to the moment they lie in bed before sleeping. Even specifically working jobs where smoking is acceptable.
IMO, tobacco is one of the most damaging drugs out there. The smoke is extremely fine and sticky so it soils the deepest passages in the lungs. It is also slightly radioactive due to its very large soil footprint (concentrates background radiation from soil). This is why you have a much higher risk of cancer even if you just chew it. And it is so addictive that you have people trying to smoke it while they’re on oxygen for emphysema.
I smoke once in a while because the social benefits outweigh the risks for me. Most of the best things in life come with far bigger risks.
Nicotine is harder to kick than most recreational drugs. That said, I wouldn't doubt he has found opportunities to "get his head on" (who knows - maybe more than one way...).