Wait, so you don't need a refinery on every planet to get full benefits?

so in other words.... say I build 3 refineries on a planet with 3 rocks, and the said planet got 4 lanes leading to 4 other planets with 3 rocks each, all these rocks will be filled by refinery ships?

Yes



Wasted resources. Say you have planets A and B connected. Putting 3 refineries on either A or B will completely fill up their resource rocks to max capacity. Building 3 more on the other won't do anything because each rock can only support 3 refineries, but you now have 6 in range.

BTW, the purpose of such a cap is to ensure that people don't spam refineries and it also ensures that you place them strategically, that is, at locations with lots of phase lanes or logistics slots. Oddly enough, spamming trade ports works beautifully. You can get well over 200 cred/sec with 15 planets/roids. My personnal oppion on the whole matter is that refineries (both the tech and the cost to build) doesn't justify them, unless you get a planet that has 4 or 5 phase lanes and they are all going to something you own (or neutrals). Otherwise, just build trade ports and buy whatever resources you need.