The "15-15-15 coffee rule," also known as Babbie's Rule of Fifteens, is a guideline for coffee freshness, stating that green, unroasted coffee should be used within 15 months of harvest, roasted coffee beans within 15 days of roasting, and ground coffee within 15 minutes of grinding to ensure peak flavor. This rule emphasizes consuming coffee at its freshest stage, from the initial harvest to the final brew, by limiting exposure to air and reducing the rate of oxidation. There are some people that believe the last 15 relates to how long you have to wait to drink your cup among others that have a few different thoughts on the definition of the 15s. Try it and maybe you can figure out what is best for you.... The 15-15-15 Rule Explained: *15 Months (Green Beans): Green, unroasted coffee beans have a longer shelf life and can remain fresh for up to 15 months from their harvest date before they start to stale. *15 Days (Roasted Beans): Once beans are roasted, their freshness rapidly declines due to oxidation. They should be used within 15 days of their roast date to enjoy the best flavor. *15 Minutes (Ground Coffee): Grinding significantly increases the surface area of the coffee, accelerating the staling process. For the most aromatic and flavorful cup, it's best to grind your beans just 15 minutes before brewing. Why It Matters *Flavor and Aroma: Oxidation dramatically changes the flavor of coffee. Following this rule helps maintain the coffee's nuanced flavors and rich aromas. *Bean Freshness: The guidelines are a simple way to ensure you're using the freshest coffee possible, from the raw bean to the final brew. *Grind-to-Brew Time: This rule encourages you to control the grind and brew process yourself, grinding only what you need for the freshest results.