My kids love the audiobooks so much they don't have time to bother each other in the back seat of the car! We listen to them every other time we get in the car (the kids take turns with me so I can listen to the radio news or my own music, too), or whenever a squabble seems it is about to erupt in a full row (I just click the disc button and there is instant peace). If nothing else, it makes me a better driver:driving:.
The kids also get may turn them on at their leisure while playing (which they usually do). I turn them on in the background while they are engaged in simple tasks (drawing, folding laundry, building legos, etc.). Oh how we love audiobooks!!! I think the only way you could really over do it is if you completely substituted them for print. The kids need a chance to see you reading print, and to read it for themselves. Plus, the snuggle factor with read alouds is important to me, too.
We have checked out soooo many from the library. I try to have at least two on my iPod, and one in the car. I have ones from CD that I ripped onto my computer the kids haven't even heard yet. And I get them for me too. I can curl up with my knitting, hot chocolate, and my audiobook at night and chill out. :mellow:I have purchased from Audible.com before, as well, and they have good quality.