I believe the L1 area would be an ideal location for such a station. While LEO-HEO is appealing launch-wise, if we want the thing to stay in the sky longer, it has to be further from Earth's influence. L1 has the advantage of being the gravitational mid-point - to reach either body, you'd simply "drop" the thing in question, with a few course-correction thrusts here and there.

Furthermore, with the call to travel to, and potentially capture and mine Near-Earth Asteroids, L1 is the ideal place to park them. They'd be close enough to conveniently access, yet distant enough to handle should problems arise. If, and when they do, simply nudge 'em towards the Moon, which'll handle the rest.

Combined with the fact that Lunar colonisation is a goal for the near-immediate future, lunar resources (dat helium-3) would be extremely useful for interplanetary travel - with enough energy and material, we could even build "shipyards", or at least orbital factories, greatly diminishing launch costs (all our shit'll already be up there)