A hot carrier ageing model previously validated on a one-stage 60-GHz power amplifier (PA) is demonstrated to be able to predict the degradation of the characteristic parameters for multistage high-performance millimeter-wave (mmW) PAs. The increase in the threshold voltage, the decrease in the transconductance, and the output conductance of the MOSFETs caused by hot carriers leads to a degradation in performance of the PAs. Consequently, by using this ageing model, the mmW PA lifetime can be extracted. A new PA is then designed, taking into account the ageing effects, and is shown to be reliable during ten years. This amplifier exhibits a power gain of 20 dB, an output 1-dB compression point of 12.5 dBm with 6.6% power-added efficiency, and a saturated output power of 16 dBm at 60 GHz.