Erin, my silver tabby was FIV-postive. She lived to be almost 19 years old and had no major illnesses until her kidney's gave out. That is fairly common in very old cats.

Guin, my other cat, had to get bi-annual vacines against FIV, but that was the only thing. She lived 6 months longer, making it until 2 months before her 19th birthday.