The time it takes for a savings bond to mature is completely based on the bond issued, so owners of a savings bond need to check the "issued to" date on the bond to see when it will mature. The time a bond takes to mature is the difference in time between its "issued from" date to its "issued to" date.
Depending on the condition of the bond, a savings bond may enter into a period of extension after it matures. This is generally a 10-year period in which the bond continues to accrue interest. Although certain bonds can continue to gain interest many years after the extension period, a bond will never earn interest for more than 40 years from the issued date.