As of 2026, Delta SkyMiles never expire, meaning your actual "miles" (the currency used to book flights) stay in your account forever regardless of activity. However, it is important to distinguish between "Miles" and "Medallion Qualification Dollars" (MQDs). MQDs are the metrics used to earn elite status (Silver, Gold, Platinum, Diamond) and these do not roll over; they reset to zero every January 1st. In 2024, Delta officially ended its famous "rollover MQMs" (miles) policy when they transitioned to an MQD-only status system. In 2026, if you earn more MQDs than required for your current tier but not enough for the next, those "extra" dollars simply vanish at the end of the year. The only way to "save" or roll over status-earning power is through specific high-tier "Choice Benefits" for Diamond and Platinum members, but for the average traveler, your "status progress" is a strictly annual race that begins anew every New Year's Day.