This paper studies the impact of the aging on power GaN transistors in switching conditions. The devices under test are commercial discrete enhancement mode gallium-nitride HEMT. We present a power cycling test platform that controls the switching conditions such as frequency , duty cycle, and gate voltage; as well as drain current and drain voltage. We have measured specific parameters before and after the power cycling in order to detect indicators for each drift effect. We measure not only the electrical parameters given by datasheet, but also the traps causing Dynamic On-State Resistance, an specific drift effect of this technology which compromises high frequency efficiency in switching power converters.