Threshold voltages (Vt) in high κ nFETs are observed to shift under prolonged positive gate bias stressing. This bias induced Vt shift (ΔVt) is referred as PBTI and is an important reliability issue. In this paper, we extend a previously proposed PBTI model to include de-trapping kinetics. The proposed model is verified by comparing calculated results with PBTI data measured over a wide range of stress conditions. Using the proposed model, an accelerated method for estimating 10 year lifetime is presented. This method does not require a-priori knowledge of parameters and uses a combination of voltage ramp and constant voltage measurements to estimate model parameters with the total measurement time < 1 hour. Using these extracted parameters and the model equations, 10 year lifetimes are estimated at different stress voltages.