Actually I think you need 30+ days to keep items. Which means that even if it's possible to use 3 buddy passes back to back, you still need at least one more day to qualify.
I agree that the buddy passes should be nerfed now that the game is f2p. I think they should keep the referal program though. You should get some benefit for convincing someone to upgrade to Gold. I have the holographic tribble and science officer, but it would be nice to have the Gal-X.
I was in a fleet pvp competition the other day and the f2p members were not able to join. Is that a restriction on f2p?