This isn't really any concern of mine for now, but I am curious for the future.. Say you already had the CTLab medal and the Genius title along with all research tiers complete, would there be any good reasons to keep your research planets? Maybe not get rid of all of them but get rid of a few and give them to lower ranking members of the legion who might need them more. Surely if you used the freed planet slots for more mining planets it would generate more credits than the research contract and of course more artifacts would only be a good thing. I can see how maybe holding onto them for use of the CTLab if you ever really need to in future which is why I suggested not abandoning all of them.

At higher ranks most of your res comes not from planets, but from crew.
There are alot of people who do drop their res planets.
Also some res planets can actually make more than mining ones.
another reason to keep res for credits is caps. getting rid of res for mining didn't work when you cap mining anyways.

I fixed your one mistake. That being said, I have found research to be lucrative for credits and like KJ said, it is great because you have two things capping so you cap slower. (IE, having 40k MP, you lose more due to caps than having 20k MP and 20k RP). And the average research planet is larger and has been research artifacts (plus no tax on research contract) than the average mining planet so it all works out.

I have sort of stopped taking them for research (have been known to take them for the arties on them through) although, I don't have the GP to abandon then. I'm using planetary data optimizers to max out the Massive or better research planets I have.

Once that's done, I will start maxing out the artifact planets I have with research. There are a lot of cross-over artifacts (artifacts that give you artifact production and research or mining like warp gates or relay towers). An optimized invisible 20x artifact plasma will still give me about 200 rp/hour at 15x.

The caps didn't occur to me and they do make sense, thanks for the input.

like everyone else said, the higher cap for research is usually going to mean more of a payout.

ive only got 36 planets listed as research planets, but 12 are actually arti planets and one is storage,
so of the 23 other planets ive got 4 exotics doing a bit of two resources, and ive got 3 plasmas that are decent enough
the ones that are just regular old research, if i lose them i purge them and say thanks, they arent really a loss, since my android scientists are replacing a very massive rich planet at the rate of 1.5 planets a week.

ill steal a nice plasma if i see it, but i wont be heartbroken if i fail either...