If you are the only one on the course and have a cart, three hours is plenty of time.
Playing on a weekend on a typically populated course, four to five hours.
Thank you for the info. I had heard a few weeks ago that it had taken him over five hours on one course, but I had no idea whether that was typical, or not. I'm sure he never hurries though. The guy has probably spent at least 800 hours (twenty 40-hour working wks!) screwing around on golf courses on our dime, all while the world burns.