When remaining useful lives (RULs) are predicted for turbines in a wind farm, decision-makers face the challenge of determining when to perform predictive maintenance. To address this question, this paper applies a predictive maintenance options model to both single turbines and entire offshore wind farms managed via Power Purchase Agreements (PPAs), considering the uncertainties in wind, the accuracy of the forecasted RULs, and discrete maintenance opportunities. The optimum maintenance plan for the turbines in a farm is not the same as the optimum maintenance plan for individual turbines managed in isolation due to the constraints provided by the PPA.