In my experience, a typical set would be between 40 and 50 minutes. I would make up a list of about a dozen pieces; if I found myself at the end of the list with time to spare, I'd steal one or two from the next set. Many possibilities for how you divide the time up, of course; some prefer longer sets and longer breaks, and vice versa.

For an hour set, I suppose I'd have about twenty songs, and might drop out one or two, depending on how long the shaggy-dog stories go on, etc.