I think that when one offers to donate a second organ or part-of-organ one of the things that the hospital DOES consider is whether the person is sort of "addicted". I think most of us feel very good (once recovery has passed) about what we have done. And while we may very sincerely desire to help someone else, the desire to repeat that feel-good time may also be in the back of our very complicated minds. Or, the desire to be admired, appreciated, etc. So while I have often joked that transplant hospitals sometimes treat potential donors as crazy-until-proved-otherwise, that may go double for second-time donors. So anyone trying to do so will have to be very patient and persevering.
best wishes,
Fr. Pat