The reliability, long-term performance and lifetime of high power diode arrays are important issues for pumping of solid state and fiber laser systems. Operation of high power arrays in these systems has resulted in greater degradation rates than the reported lifetime data. We report on lifetime testing of a commercial high power array using an automated diode array reliability experiment. This computer controlled setup operates the laser array 24 hours a day in a cyclical format of 10 minutes on and one minute off. The array currently being tested was operated for more than 2500 hours at which time it experienced a sudden drop in power. Analysis of the array and the data suggest that the micro channel coolers corroded and that a sudden plugging of one or more channels caused the failure.