From an email sent by Delta Airlines:
You now can earn miles without worrying if and when they will expire as we have eliminated our mileage expiration policy – no asterisk, no fine print, no ifs, ands or buts.
So regardless of your future SkyMiles activity, redeem your miles whenever you want for Award Travel to 350+ worldwide destinations, car rentals, hotel stays, newspapers, magazines and one-of-a-kind auction packages.
We are proud to be the only major U.S. carrier without mileage expiration.
Visit delta.com to learn more about your SkyMiles benefits and explore the many ways you can earn and use your miles.
You’re the reason we fly!