There is a play on the word "mothballed" here. "Mothballs" are a type of pest repellant used to protect things such as wool garments. "Mothballing" is a verb used loosely to mean retiring something from active use due to age or irrelevance. So an old wool coat, which would be protected from pests such as moths with mothballs, is retired because it is too old or worn out, that is to say it is "mothballed".
OLD WOOL COATS never die , they just become mothballed .