When stored in the freezer in a tightly sealed container, lemon juice is good for at least 3 to 5 months, sometimes even longer. To tell if lemon juice is no longer good, look for changes in color, smell or taste. If it is a darker color than normal, or doesn't have a citrus smell or taste, it is likely turned bad.
Most people use lemon juice in very small quantities, therefore freezing lemon juice in the original bottles is not recommended because it would require unfreezing and refreezing, which is unhealthy. Instead, it is recommended to freeze lemon juice in ice cube trays or freezer bags so the quantities are smaller and can be used as a single serving.