I completely agree with not adding more sawdust/ grass clippings to the old pile, but we've "merged" them into a pile where the old and new are back to back, if that makes any sense. Our logic for making a "line" of compost is that we can turn it more easily. We made it Saturday, soaked it, and this morning I got a nice warm feeling off all parts of it so definitely we have something this time. In addition to mixing more we also stomped down the mix so it wasn't so fluffy, added kelp meal and some manure, and again, watered it as we went.