If you can't asses a candidate in a 20 minute conversation and 45 minutes in the air you are in the wrong business.
In the days when a PPL Skill test was just a GST that was probably correct, but today with the implimentation of European Regulations all of the required elements of a PPL Skill test, which is 60% Navigation, then it is simply not possible to conduct a PPL Skill test in much less than 2 hours 10 minutes.