Front end accessory drive (FEAD) system explained in this paper is a sub-system of an engine. In FEAD system, a poly-v belt is used to drive the alternator and water pump by transmitting power from crankshaft pulley. In a new vehicle development program, durability targets of FEAD system are based on required life of poly-v belt, its static tension readjustment interval and replacement frequency. To meet these durability targets following methodology is applied in design stage:- 1Simulation of FEAD system to calculate the theoretical life of belt2Part level testing of belt as per SAE J2432These methods give sufficient information on belt durability. However in actual usage, certain failures are prone to happen and enormous difference is always observed between theoretical and actual life of belt.This paper describes the traditional stair-case approach followed to optimize the FEAD system based on the outcome of durability tests. Component level test results of poly-v belt, like belt elongation and belt wear verified in actual engine level testing for improving the belt durability.General test duration for durability is approximately 40 working days depending upon test hours. This paper describes the check points and criteria to predict the performance of 40 days of durability test on the basis of initial 10 days (which is very practical) for evaluation of design changes thereby saving significant amount of development time.