It largely depends on the model, size, and load of your True Freezer. Generally, it takes a few hours for your True Freezer to reach its optimal operating temperature. Keep in mind that it's quicker if you're putting in items already chilled as it will help to maintain the temperature more effectively. Some sources suggest that it can take up to 24 hours for a new freezer to entirely freeze fresh items placed inside. Always check the user manual for accurate information regarding your specific model.