This is a good thread.I have a question about refineries. Should I build refineries on adjacent planets? I mean if a refinery uses resource extractors around its planet (A) and the adjacent ones (B and C), does it mean that if I build another refinery on B it would take over the resources around B (i.e. refinery around A won't use them anymore) and then the total output will stay the same?
If you look at your extractors, they have a "refinery quota" stat on them. Thats the number of refineries they can service. I believe for normal extractors its 3.
So yes, if you have a refinery and you build another one next door, the two can overlap. You'll see refinery quota 2/3, and they both work. If you were to build two more in adjacent systems, you'd see 4/3, and one of them wouldn't be processing any resources from that extractor.
eg:
A -- B -- C
If you build refineries at A, B, and C, A and C's extractors will be at 2/3. B's will be at 3/3, but they all work (A will get both A and B's resources, B will get resources from all three).
But if you had this:
A -- B -- C
|
|
D
If you built refineries in all four, system B would be at 4/3, and one of the refineries (probably the last one you built, so the one in D) would get nothing from the resources in B.
Hope thats clear.

edit - Trying to get things to line up properly, D should be connected to B.