[garciansmith]

My grad school supervisor (requiescat in pace) lamented the decline for a similar, very minor reason: he always thought that getting up, going outside, smoking a cigarette, and coming back in was the perfect amount of time for a class break. Ten minutes was too long, five too short.

[OptionOfT]

My mom (who smoked, and quit) explained to me that when she was growing up, the teachers would still smoke in class! That was in the 1959..=1964 timeframe.

[bigstrat2003]

One of my college profs said that when he was doing his undergrad in the 80s, he used to bum smokes off his professor in class. It definitely lasted for quite a while.