Consider a two-echelon repairable inventory system consisting of a centeral depot and Multiple stocking centers. There are two kinds of defective, type A defects must be repaired at centeral depot, and type B defects at stocking centers. The centers provide parts replacement service to customers and the depot fills center replenishment orders on a FCFS basis. Type A defects that are received at the centers are passed to the depot for repair and depot inventory replenishment. For this system, existing models (for exemple, METRIC model) usually assume that the depot replenishment lead times (DRLTs) (for type A defects) are i.i.d., which however, does not fit well into the service part logistics system, that motivated this research. Because the DRLTs consist of ti,e sum of repair times, defective return times and transportation times, they are different across stocking centers which are located globally. We study the impact of such center dependent DRLTs on system performance. We show that for such system. using the i.i.d. DRLT assumption introduces errors in estimating system performance.