The main goal of a band should be keeping the audience engaged. With three hour shows that can be difficult, if the energy goes up and down and up and down and up and down. I think a good show always has some kind of dramatic arc or balanced rhythm.
You can have too much of a good thing. Though, obviously, it differs from person to person. When I saw them in 2017, I think three hours was kind of pushing it. But each to their own