Don't forget that back in the 80's it was comon to have aircraft arriving and departing on 11L/29R, 11C/29C, while circuits were going on on 11R/29L. You also had multiple helicopter movements occurring at the same time.
It was that busy back then, that at times you had to ring up the tower and book in if you wante to do circuits.
The big schools (Royal NSW Aero club, Navair, REX/Skywise, AFTS and Illawarra/Chieftan) had large fleets 10-20 aircraft and you still had to book in 4 weeks ahead to get your instructor and aircraft.