He may have originally been on a quest, but as he was loosened up from his Harvard stuffiness, he opened to all kinds of experiences and was seduced into hedonism.
He was (at least initially) against the Merry Prankster's form of acid ingestion (unrestrained quantities in a warehouse party with lots of strangers). The original posters even asked "Can you pass the acid test?".
I seem to recall reading that Cassady was running around with a gallon jug of electric kool aid.
It was almost classism that the cultural elite and trust fund kids could take it with Leary but not the masses. Leary alleged that even JFK consumed LSD with one of his followers. The last thing I recall hearing about him before his final year was getting busted for smoking a (tobacco) cigarette at the Austin airport.
He froze his head cryogenically (and the procedure was recorded for the film Timothy Leary's Dead). Even still, I don't think we'll be seeing him again.
Just as the Pranksters sought to operate "normally" while under the effect of LSD (working the sound board controls, etc. at the Acid Tests), some of the followers of trepanation make attempts to read complex texts while their thinking processes are altered (I recall someone in EKAAT saying that reading a book was an "isolating" experience though, so the Pranksters seemed to frown on such activity in the group setting). The Merry Prankster's use did not seem to be purely for the feel good effects. Its usage on the bus was somewhat regulated, a woman who was sneaking doses lost sense of herself and all decorum and was sent back home; the video I've seen shows her at MacMurtray's home (although the footage of her attempting to breast feed one of his kids was not recorded, the camera operator felt embarassed to capture that moment) as well as her losing it at the Houston zoo (doing handstands and the like).
But on the plus sinde, the counterculture did spell the end of those horrible looking crewcuts (although they are now making a comeback again).