What is the 15 15 15 rule for coffee?

The rule goes like this: green coffee lasts about 15 months before it goes stale. Roasted coffee lasts about 15 days before it goes stale. ground coffee lasts about 15 minutes before it goes stale. A reminder – fresh roasted coffee’s rule of 3’s. Ground coffee – 3 minutes, roasted coffee – 3 weeks, raw coffee – 3 years.