Korea’s 2026 ESS central contract market (1,180 MW, opened 22 September 2026) introduced, for the first time, a 25-year contract on Jeju for facilities capable of two charge/discharge cycles per day for 25 years. A longer contract lengthens the retention period for cell-level Traceability records. Under an assumed scenario (8-year system replacement cycle), the contract term grows by 67% but Traceability system migrations triple from one to three, while one generation of cell records is only about 15.9 GB. The design constraint of a 25-year contract is not storage but genealogy breaks at each migration.