I've done a couple jobs for free just to see how long it takes. A typical driveway seems to take about an hour (not counting set up and take down).
I took some before and after pictures.
BEFORE
AFTER
This Job was at the church. There were several areas that needed to be pressure washed but this was the only place that had a faucet I could turn on. The rest needed a special attachment. I decided to clean the wall, too, since it looked really bad.
BEFORE
AFTER
I'll usually come back the next day to take the "after" picture so that the ground has had time to dry so you can really see the difference.