Last night I played a show with my band, for an audience of salespeople and retailers involved in the Canadian shoe industry. It included the longest single set of music we've ever performed: two hours and five minutes, one song after another, without a break.
Generally, we decide when we take our breaks, but you read the crowd. We'd already left the stage once for half an hour, and the audience had thinned out considerably (while summer, it was a Sunday night). We knew that if we took another breather, however short, the rest of the guests might take off too, and playing for five or six people drains your energy as a musician like you wouldn't believe. So after an hour, we kept going, and going, and going...
By the time it was over, my right hand was tingling like it was recovering from falling asleep, and today I'm sore all over. But they loved us.
I know why we take breaks at most shows now too.