The lifespan of award miles varies significantly depending on the airline's specific policy, which typically falls into three categories: "never expire," "soft expiration," and "hard expiration." In 2026, many major U.S. carriers like Delta, United, Southwest, JetBlue, and Alaska have adopted a "never expire" policy, meaning your miles are safe as long as your account remains open. Other airlines use a "soft" model, where miles expire after a period of inactivity—usually 18 to 36 months—but the clock can be reset by any earning or spending activity. Examples include American Airlines (24 months) and British Airways (36 months). Finally, some international carriers like Singapore Airlines and Emirates enforce a "hard" expiration, where miles expire exactly 36 months after they were earned, regardless of account activity. It is crucial for travelers to monitor their accounts, as many airlines send only minimal warnings before miles vanish. For soft-expiration accounts, a small purchase through an airline's shopping portal is often the easiest way to "save" miles from disappearing.