The last 8 day conventions were held in 1969 giving way to the 5 day, then the 4 day, and now the 3 day district convention. Circuit assemblies at one time were three day bginning on Friday evening, Saturday morning was for field service. This gave way to the single two day Circuit Assembly and one day Special Assembly Day.
I hated those 8 day conventions. Too much, too long, too boring listening to people like Knorr, who was no great speaker drone on and on and on. BTW Knorr always went overtime on his closong remarks at the conventions sometimes by more than an hour. Why he thought people would love to hear him dribble was a wonder. Met him backstage at a convention once when I had a part, what a pompous ass he was, acted like the world shoould bow to the earth for him.