How long is jello cook and serve mix good for after the 'best by' date?

Jello cook and serve mix can typically remain good for a few months beyond the 'best by' date if stored properly in a cool, dry place. While the mix may lose some quality in flavor and texture over time, it is generally safe to consume if there are no signs of spoilage. Always check for changes in color, odor, or clumping before use. However, for the best results, it's recommended to use it before the 'best by' date.