A container of unopened ricotta cheese might stay fresh for two to four weeks. However, it depends on the specific batch. The expiration date is a good indicator of how long your ricotta cheese will last. If you've opened the container, it's up to you to determine whether or not your cheese is still good. Signs ricotta cheese has gone bad are if it’s covered in mold or black spots, if you notice a change in color, or turning sour (which you can easily discern by smelling it - it will have a strong odor).