Heroin/opiates are a bad example. Addicts with a steady supply or chronic pain patients are able to go years without skipping a day. I can't track it down right now, but I read a study a few years ago from some European county where they decided to try just giving a group of addicts all the heroin they wanted. The majority used every day, held down jobs, stayed out jail, and were relatively healthy. Of course government spending money to give addicts drugs was an outrage., so the program got shut down early.

Hallucinogens would be a better example, there would be no way to function in society if you were constantly on one.