I have heard that if an older cat has feline leukemia, it can be manageable. I have a friend with a cat who's 14 (I think) and he's had this for quite a long time. She has to keep after his teeth and gums, and uses a holistic vet which seems to work for her. Good luck!

FLV is more contagious than FIV. You might want to give your negative cat the FLV shots, even though they are only about 75% effective, it's better than nothing.