I have one playthrough that I've completed 8/10 spheres on the first star, and everything is automated to the point that I could manage to build all 640 spheres, but.... That would take me 1.5 hours to gather the resources, turn on the rail guns and rockets for 30 minutes, and shut it down again to gather resources for the next sphere.

Before you ask, that 30 minutes doesn't include pausing the game and adding in the next shell, but after the first system, I could copy paste each other systems shells. The 30 minutes is building the frame and capturing all the solar sails. I generally average ≈100 solar sails wasted per shell, hence the stages.