I do two karaoke shows a week at the King of Clubs in Mountain View.
I run from 8:30pm until around 1:30am, and up to a few minutes from closing on the busier nights. This is the busiest show of the week. We generally draw quite a crowd - singers will have a large, appreciative audience, but even arriving early and staying all night may only give you three songs.
I run this show from 8:00pm until some time after 1:00am. Again, if it's busy enough, I may run until just before close. This is a considerably less busy night than Thursday, with a quite variable crowd, and a singer can expect anything from 5 to 12 songs in an evening if they stay all night.