The initial 100 or so questions usually takes over an hour. Then another 30 to an hour on the box. Most that I have passed give the test three times, if deception is shown on the same question twice, then you are given it a third time. If you show deception on lets say two separate questions, but only on one of the tests, then you will only be administered two tests.
I PURPOSELY showed deception on "are the lights on in the room"? (an obvious control question) and believe it or not " have you ever stolen anything in your life"? (Another obvious control question) MOst agencies know that you have stolen something like a pen from work etc, and you're not going to remember all of these times, thus most likely show deception, which makes this question a very good control.
One skilled in taking a polygraph will know that you WANT to show the highest level of deception that you can on these controlled questions. Those of you familiar with the polygraph will know why.