Are you sure that isn't cirrhosis?
That sounds more likely with 6 month interval ultrasounds?
I found an excellent website where you make find a good answer.
http://en.allexperts.com/q/Life-Support-Issues-2065/Dying-Liver-Cancer.htm
There are so many extenuating factors, it is difficult to put a number on it. I, too, read that prognoses are rarely good. But treatments are improving all the time. My father is terminal with liver cancer that metastasized from the colon. He has "been given" two months, but that really isn't for us to say, is it? : )
Best of luck,
SweetHaven3