The flat surface cleaners are great for large areas although you usually need to go over the edges and possibly some cracks or heavy stains with the turbo lance but still a lot quicker than a lance alone. Impossible for me to say how long for the average drive as it depends on the surface, the soiling, the layout etc but try not to rush the work. In this line of work it is a bit like the hare and tortoise, you will get better results from taking your time and that will probably lead to more work.
Good luck.
