The longest layover I had and I will still have is about 4.5 hours. I fly two times a year from USA to Yugoslavia (I'm a foreign exchange student) and have to change three flights. I usually wait 4.5 hours in Minneapolis or Amsterdam to board on the next plane, which is not that bad because both airports are big and there is stuff to do. If talking about longest delay, it was last year when my flight from Amsterdam to Minneapolis was two hours late. I missed the plane and had to spend one day in Minneapolis because there was no flights for Minot ND after 22:30. It was not bad, I mean what is wrong with spending one day in Minneapolis with paid Hotel and food. I was maybe little bit scared because that was my firs time in the USA. However, it was great experience if not taking into consideration that I had to pay $25 for taxi, because Hotel shuttle was overcrowded.
(Hope there are not too many grammatical errors. This is my first year in the USA and I am still trying to gain better knowledge of English.)