No need to get agitated. Some people enjoy sitting in the car for multiple hours, some people don't. I found it changed for me as I got older.

However, about those 20 minutes — this, again, is a misconception. Stop at a busy rest area or a gas station and actually start your stopwatch. If you are a single male, it might take you shorter. If you are with a family, 20 minutes is pretty much the minimum.

Really depends on the air quality inside (and indeed outside) the car.