When I first started, the cardbacks had filecards on them. I'd cut them out and throw everything else away.
Then they stopped doing filecards and I would throw everything out.
Then came Jedi Points. Since then, I have saved every one hoping for some cool mail away promotion that would actually make saving them worthwhile. Well, as we all know, that didn't happen. I'm stuck with a box of JPs that are absolutely worthless. And you know what? I still save them, hoping that someday they might be useful.
As for vehicle boxes, I saved almost every one, including all packing items (cardboard, bags, etc.). At the time, I was living in an apartment and knew I wouldn't be there forever and eventually I'd have a house. Keeping the boxes made for easier transport and storage.
I save all my Lego boxes as well, not including the bags. Most of them were put together, then I ran out of room. So I broke them down and put the pieces in ziploc baggies in their original boxes. That way, when the time comes, I know everything is where it should be.
Now since the Saga cards were each unique and numbered, I have saved all the cardbacks. Threw away the bubble and the inserts went into my box of Jedi Points, since the JPs were on the bottom of them and no longer on the cardback itself.
So what does the mundane reply mean? Probably that I'm somewhat anal retentive, but no where near what Matt and some of you others are.