We have onions from our garden and we keep them most of the winter at room temperature. Some years they last until February. Never throw over leftover onion. I have a covered bowl we keep the leftovers in the refrigerator in. Some years the onions don't seem to keep as well so I chop them all up and freeze them. They are just fine for cooking. We also have a hard time using up a stalk of celery before it wilts. I chop it up and freeze it also.