There was the ISF, once...and unmanned platforms.
For instance, various platforms, each with specific tasks, could be orbiting Earth, far enough from each other not to interfere, but close enough so each can be accessible to some unmanned shuttle in one trip.
Those platforms would be each one behind the other and to us on Earth, they'd look like a string of pearls in the sky.
(I've thought about it too but then, one of the platforms could be unmanned but man-tended while another would be permanently manned and the Shuttle was still active).
Nothing prevents those platforms from being completely unmanned, though.