I agree with the "when you don't have any more room" reply. I keep lots of small scraps but some of them are kept in a large and small trash bucket. When I have a small project, like one I'm working on now, I look at the scraps I have laying around, sometimes they are on the floor. Many, many, times I make something out of scraps less than a foot square. Sometimes less than half that. But once in awhile, I need something to get a trash pile started or the accumulation gets to be too much and I clean up - a little.