Four hours was the most I did.
Was playing at a Chicago club known as The Drink. That night a promoter was throwing a party in the back area, and most of the DJs he booked were used to playing short sets of Chicago hardhouse. Granted it was around 1999 or 2000, and Chicago hardhouse became passe to many clubbers while I was the lone wolf playing the more “newer” sound of trance.
So the other guys played short sets, and I seemed to win the crowd over with trance. The promoter asked me to play longer and I did…til closing. Great night.
Shortest set I did was 20 minutes. It was supposed to be an hour, but I was scheduled as the LAST set of the night at an all-night rave. 5AM til 6AM. Unfortunately everyone decided to call it a night at the beginning of my set and within 10 minutes everyone left. The promoter decided to just call it quits and close up shop. He made it up to me at another event with a better spot, but I was disappointed that night.
Generally though when anyone offers me a 30 min or less set I’ll tell them to take that time and disperse it among the other DJs so there’s transition time.