This paper proposes a methodology to analyze the long-term degradation of a wind turbine drivetrain using a gain-scheduling control strategy considering the variation in the wind conditions. The degradation in the transmission is modeled through a simplified dynamical system based on contact mechanics, employing the dissipated energy as an indicator of the degradation in the shaft. In addition, a gain-scheduling control strategy is considered to assign a control gain according to the wind flow conditions. The long-term simulation is based on the accelerated degradation due to turbulent wind compared to the laminar flow. Numerical experiments were considered to illustrate the proposed approach, assuming a 2 MW variable speed-fixed pitch turbine with a horizontal axis and fixed gearbox.