Forever Stamp Fact Sheet - USPS
about.usps.com › news › fact-sheetsIn 2011, all first-class one ounce stamps became forever stamps with the exception of stamps in coils of 500, 3,000, and 10,000. As the name suggests, Forever Stamps can be used to mail a one-ounce letter regardless of when the stamps are purchased or used and no matter how prices may change in the future.