The site I'm at now has an area for bigger tents which is where I'm pitched, it seems common here for the husband to drive down in his van whilst the wives bring the kids in the car. Some people have a huge amount of stuff!
We've actually taken 3 cars between 5 of us before! Hubby and I with most of the camping stuff and dog, my daughter and her fiancee took their car as no room in ours and our son is far too cool to travel in the same car as anyone else so he insisted on taking his own. We didn't need the roofbox that time though!
All the time. Started off because Ricahrd would join me from work, then one year he was working nights, was getting a few hours kip and then joining me, so we split the gear, and suddenly we had space all round. Now it means he can smole withou my moaning at him. I can listen to my music, or occasionaly one of the kids discs. I was also more amiable about stopping when the kids needed the loo - didn't make a major drama out of it.~For me its worht the extra fuel for the general all round comfort and stress free trvel.