Here's my two cents about the whole green/blue/green feed/breed cycle:
I don't think it's likely that the inhumu go back and forth as often as people have previously speculated. In both books I believe, Horn says that even when the two planets are at conjunction, the trip between is dangerous and many imhumu do not survive (forgive me for not having and exact reference.) Judging by the danger and said low success rate, I think that inhumu must be able to obtain enough blood and be able to breed on both plants.
Just my theory
-Mnemonic