Everytime I've seen KISS (3 times thus far). Once was in the Toyota Center and ended around 11pmish. Second and third was at The Woodlands and was outdoors. First woodlands show they had to turn down the volume after 11 but finished the last two scheduled songs. Second one ended on time around 11 or so.
Guess it varies from place to place.
Also I don't see her cutting the opening act piece. I don't see anyone doing that. It's a great way to help smaller acts get noticed as well as warm up the crowd a little.