A. Live lobster is greenish/brown. The lobster becomes red during the cooking process. Q. How long can I store live lobsters before cooking them? A. Live lobsters can be kept for approximately 12 hours under refrigerated conditions although most will survive for at least 24 hours. Q. How long can you keep cooked lobster in the refrigerator? A. A cooked lobster can be stored in the refrigerator for up to 3 days. Q. What is the difference between a hard-shell lobster and a soft-shell lobster? A. In the summer lobsters shed their shells so that they can grow. Once the lobsters have shed their old shells, there are new, soft shells underneath.