No, United Airlines (UA) MileagePlus miles do not expire. United made this change permanent in August 2019, following a trend among major US carriers to eliminate expiration dates on loyalty points. This means that as long as your account remains open and in good standing, your miles will stay in your balance regardless of how much time passes between your flights. This is a significant benefit for "casual" travelers who might only fly once every few years, as they no longer have to worry about making a small purchase or booking a flight just to "reset the clock" on their points. However, it is important to note that while the miles themselves do not expire, United reserves the right to close accounts that have been completely inactive for a very long period (typically several years) or in cases of fraudulent activity. For the vast majority of users, the "no expiration" policy offers complete peace of mind for long-term travel savings.