Postage stamps never expire due to the passage of time. However, stamps that have been used or postmarked cannot be reused. Additionally, the price of postage may be raised, making it necessary to use additional stamps to meet the new rate.
Forever stamps, nondenominational stamps issued by the USPS, do not have a value attached to them. However, postal customers can continue to use forever stamps regardless of whether or not postage prices go up, as these stamps do not require additional stamps to meet the current price of postage. A forever stamp has no expiration date and can be used to mail a letter weighing up to 1 ounce.