According to the manufacturer, reddi whip is good for four weeks after the best by date. However, many users find that it is still good for several weeks after that date. Once the can is opened, it should be used within a week.reddi whip is a whipped cream product that is sold in a can. It is made with milk, cream, sugar, and stabilizers. The product is shelf-stable and does not require refrigeration. The can has a "best by" date stamped on it, which is the date that the product is guaranteed to be of the highest quality. After the "best by" date, the product may still be safe to consume, but the quality may have decreased.