Lori, I think it depends on what you do besides just piecing blocks...small pieces are good for paper piecing, or foundation piecing. I just learned this and love it.
Also, anythign too small to use, I put in a special bag, to use for stuffing for items you might want to make...
I want enough to make a dog bed, actually 2 dog beds.....and am getting there fast. I also save the pieces of batting that are not useable, for the same purpose.