User blog comment:Goku259/energytainer/@comment-1743498-20120625175932/@comment-1743498-20120626123050

Well, technically, you can still move the Dyson spheres around away from the solar system. Even if they are not next to the stars, they still retain their energy for a long time. Depending on how big the mech is and how efficient it is at using energy, its "battery life" could range from several days to several weeks.