A method of operating a wind farm including a plurality of wind turbines with a plurality of turbine components comprising a first and further turbine components, said turbine components subject to degradation, comprising - predicting, for a turbine component of a first wind turbine and for each of a sequence of time intervals (t 1.. t N1) into the future, based on a sequence of first turbine control input values (u 1 (t 1)... u 1 (t N1)) including a component maintenance action at a maintenance interval t M1, a component life index L(t) of the first turbine component, - determining a sequence of optimum turbine control input values (u 1 *(t 1)... u 1 *(t N1)) including a) an optimum maintenance interval t M1 * for the first turbine component and b) optimum maintenance intervals t M,j * for each of the further turbine components that optimize an objective function J(u) depending on the component life index L of the first turbine component and on component life indices L j of the further turbine components, and - operating the first wind turbine according to at least one optimum turbine control input value u 1 *(t 1), characterized in that the method further comprises - predicting the component life index of the component based on a sequence of second turbine control input values (u 2 (t 1)... u 2 (t N2)) of a second wind turbine electrically connected to a same branch of a collector grid of the wind farm as the first wind turbine, by evaluating electrical interaction between the first turbine and the second turbine, and - determining optimum first and second turbine control input values u 1 *(t), u 2 *(t). - predicting, for a turbine component of a first wind turbine and for each of a sequence of time intervals (t 1.. t N1) into the future, based on a sequence of first turbine control input values (u 1 (t 1)... u 1 (t N1)) including a component maintenance action at a maintenance interval t M1, a component life index L(t) of the first turbine component, - determining a sequence of optimum turbine control input values (u 1 *(t 1)... u 1 *(t N1)) including a) an optimum maintenance interval t M1 * for the first turbine component and b) optimum maintenance intervals t M,j * for each of the further turbine components that optimize an objective function J(u) depending on the component life index L of the first turbine component and on component life indices L j of the further turbine components, and a) an optimum maintenance interval t M1 * for the first turbine component and b) optimum maintenance intervals t M,j * for each of the further turbine components that optimize an objective function J(u) depending on the component life index L of the first turbine component and on component life indices L j of the further turbine components, and - operating the first wind turbine according to at least one optimum turbine control input value u 1 *(t 1), characterized in that the method further comprises - predicting the component life index of the component based on a sequence of second turbine control input values (u 2 (t 1)... u 2 (t N2)) of a second wind turbine electrically connected to a same branch of a collector grid of the wind farm as the first wind turbine, by evaluating electrical interaction between the first turbine and the second turbine, and - determining optimum first and second turbine control input values u 1 *(t), u 2 *(t).