I've been collecting large boxes and storing them in our garage for months for the girls and I to play in. I envisioned us dragging them to the front yard and making some kind of giant box castle complete with lots of tape and paint. I thought we'd leave it up for about a week and then recycle the whole thing. However, things worked out much simpler than that!
We occasionally pull the boxes out of the garage for a few hours and play and play and play. Then we drag them back in to save for another day. We've had a wonderful time, but Elliott is not thrilled about his garage being cluttered with large cardboard boxes!