When Bodine was headlining a concert, they often played two sets with a break in between. Anno 2011, concerts are rarely done that way: one set only, If you're lucky bands will play a spontaneous encore, but there is no time to let off the steam, get a beer or a smoke, or evaluate the half time performance of a band.
What would you prefer?

I like 1 set. If you have 2 sets, when the band has luck, the audience has just warmed up if necesarry and then this breaks down as of the break.

I am inclined to agree. However, I often find that the beer supply stagnates halfway through the concert. That is an issue to be dealt with yet. I've seen personnel with backpack beer taps drudging through the audience, but that's far from ideal. They interrupt the audience and don't like it when you lift them up for a bit of crowdsurfing.