I used to do this at my old office, the record is 27 minutes I think is was the yellowpages guy. My boss thought is was funny until I did it to him one when he called in and I had enough guys in my office to sound busy and I put him on hold for 10 min.
LOL. We do it at work sometimes too. We have some who have called so many times that we know the number on the i.d.