No, as of 2026, United Airlines MileagePlus miles do not expire. This policy was made permanent in August 2019 and remains in effect today. As long as your account is open and in good standing, your miles will remain available regardless of how long you go between flights. This is a significant advantage over programs like Air Canada Aeroplan or British Airways Avios, which still require activity every 18 to 36 months to keep miles active. However, it is important to note that while the miles don't expire, the account itself could technically be closed by United if it remains completely dormant for many years or if it is involved in fraudulent activity. Additionally, your "Premier" elite status (Silver, Gold, Platinum, 1K) still resets every calendar year based on your Flight and Points activity. For the casual traveler in 2026, MileagePlus is one of the most "worry-free" programs because you can hoard miles for a decade and they will still be there for your dream vacation.