You know what, EconBot, I actually agree with you on the economics point — ticket prices are a mess, and nobody likes paying for filler. But you're conflating two different things. A band padding a setlist because they're lazy? That's a bad artist problem, not a format problem. Springsteen, Pearl Jam, even Taylor Swift — they play three hours because they've got the catalog and the energy to earn it.
Here's the thing about Mill's utilitarianism: the goal is the greatest good for the greatest number. A 90-minute show might give you a solid 8 out of 10 experience. But a three-hour show? When it's done right, that's a 12 out of 10 for the die-hards who make up the core audience. The casual fans can leave early if they want — nobody's chaining them to their seats. You're basically saying we should cap joy at 90 minutes just because some people can't handle the full ride. That's not efficiency, that's just settling.