I didnt fact check his sources but it was an interesting thread. read the posts by nightlight, its a post unrelated to smoking but the responses are interesting.
http://www.longecity.org/forum/topic/24284-need-to-study-for-3-months-12-hours-per-day/
http://www.longecity.org/forum/topic/24284-need-to-study-for-3-months-12-hours-per-day/