Depends on the artist. Three hours is a good estimate (30 minutes for the opening act and 90 for the headliner).
The show I was at last night got started around 9pm (tickets said 8:30, so par for the course) and went until 2 am or so.
Anywhere from two to three hours of actual show time. Doors normally open one hour before the show. First set/opening band is about an hour on average and then a fifteen to thirty minute break than the second set/headlining band will play for about two hours on average. This is a general layout of the shows but the shows can very. Special occasion nights can last longer and some shows may last shorter. It really depends on the band but the above is what you can expect most of the time if not almost all of the time.
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