Audio books were a lifesaver on road trips (three or four days out and three or four days back) when our children were young, beginning with the old Disney Listen and Look books before they were old enough to read. Then they graduated to audio books. We accumulated quite a collection of the children's classics and more that kept them happy in the car for years. They'd listen to them only in the car and only on vacation and looked forward to it every year.
Now that Mr. M and I are alone on our road trips we listen, too, but only on vacation. We listened to several this year, over the 6000 miles ...
The rest of the time I prefer curling up with a good book.