Time on site depends on the number of runs, how easy the chambers are to locate and lift, and whether the drains need jetting first — a silted pipe has to be cleaned before the camera can see anything useful.
If chambers have been paved or decked over, locating them adds time. Knowing where your manholes are before the engineer arrives speeds the job considerably.
Ask for the turnaround time on the report when booking, especially if you need it for a purchase deadline.