Actually, you are right, I was talking as if the shades are just orbiting the Sun. L1 orbits do require station keeping. Perhaps you could cheat a bit by maki

Actually, you are right, I was talking as if the shades are just orbiting the Sun. L1 orbits do require station keeping. Perhaps you could cheat a bit by making the shades black or oscilating/slanting them a bit forward/rearwards as to do the station keeping with very little fuel? Or shaping them like a lense to direct most light away from Earth, but not to experience too much net force? Or they are just designed to be expendable?