Normally the C152 to PA20-180 checkout at the club I instruct at is about an hour in the air.
However there is about three hours on the ground looking at the technical aspects such as W&B, aircraft performance and the Avionic system.
As the PA28-180 is the first aircraft that the guys will fly that can take them distances that can make fuel consumption and engine management critical and they can load the aircraft outside the limits while also being well away from the eye of an instructor we like to make sure that the guy is not going to make any stupid mistakes.
As the pilots have been trained to fly the C152 IAW the manual speeds we have no problem with them flying the PA28 at the correct speeds so the actual flying of the aircraft is not a big part of the conversation.