Wish I'd done this a long time ago. I bought a 5Kg bag of "crumb" from a foam shop for £13 and with a little nifty stuffing and restitching have revived all our sagging back and arm cushions in less than an hour. It's taken years off our ancient sofas! together with our sofa savers, we'll get another few years from our pair yet. (Scarily satisfying!)