I have the kids put all their precious creations in a scrapbook storage box labeled with the month. I start a new box each month, and the old box works as an archive. The older box (in the photo, December) gets moved to cheaper real estate (basement, under parent bed, etc) and I have a month to pick through it for a few gems. The rest goes to recycling, and since it's been 6 weeks at that point, I don't worry about a kid coming to me to find some old piece of art.
