Like people have said, every detail is different. I tend to call myself a paint polisher more than a detailer, simply because that's what I spent the most time doing. In a given "detail" that I do, I will spend about 1.5 hours washing and claying (an average sized sedan). Figure another 30 minutes to an hour to fully tape off the car. I will also spend the last hour waxing (waiting for it to dry--and doing minor clean up, dusting, vacuuming inside, dressing) during that time. Usually I need atleast another hour for final cleaning--cleaning any rubber seals of polish, etc..So 4.5 hrs is what I need to start and end a job. Between that is polishing. How much polishing does a car need??
Sometimes a car only needs a few hours of polishing. Especially if it's silver and the owner just wants it looking shiny again. But then sometimes you have owners that want their silver car to gleam at night even under a street lamp. Making silver flawless for night viewing requires extensive polishing. I prefer to work in a dark environment lit with small halogen lamps so I can see where the swirls are. This might be a 6 to 8 hour process here--combine that with 3.5 hours of prep and finishing.
I've had numerous discussions with detailers who do 2 to 3 hours "Completes". It's a rotary job followed by a glaze to fill in their holograms. Quite often, I get these kinds of cars where the owner was highly dissatisfied and then found me to fix those mistakes. I got one today--a black BMW.