One thing I try to be careful about is making sure my car kit remains accessible.
When packing for a trip, be it camping or otherwise, I always take out my car kit, load up the truck and lastly put the kit back in so that its easily accessible. I figure it's silly to have it buried if and when I actually needed it.
I'm on the oposite scale: My car kit is burried in the wheel well under the cargo compartment (classic estate car configuration, with a mini sized spare tire). And yes, I've had to dig EVERYTHING out to get to my skid plates (once, stuck in the mud) and to my towing rope (once, stuck in the snow). That's TWO times in, I don't know, 9 years that I've had cars with this particular configuraton.
Yes, it's a hassle to take everything out when I need my car kit. But I have the convenience of not bothering about someone else removing my kit and forget to put it back in. I also have a "clean" cargo compartment into which I can cram stuff.
I should add that I have crammed stuff elsewhere into smaller compartments as well - easy accessible even with a fully crammed car. Such as my 1st aid kit, reflex vest, some basic tools, flaslights, toilet paper, cell phone charger.