Test driving a car for an extended period will allow you to get much more familiar with it than you would with a 30-minute test drive. Some benefits include:
Driving around your local area: Instead of being limited to streets around the dealership, you can drive the car around your own neighborhood.
Driving on different types of roads: Take the car on highways, residential streets, hilly areas, and even dirt roads to see how the car drives.
Making sure it fits everyone & everything: Drive with your family to ensure everyone will be comfortable on trips. You should check that you can fit anything else you'll need, like car seats, dog crates, and luggage.
Test the car without a salesperson: Taking an intro test drive with someone from the dealership allows you to ask questions about the vehicle, but you may feel some added sales pressure while driving. Testing the car on your own can make you feel more relaxed as you evaluate whether it's the right fit for you.