Hi Julie
So sorry to hear about your Mom, and your brother too. Very sad.
My Mum was also stage IV at diagnosis. Her doctors painted a pretty grim picture, but she did very well for 18 months, and survived over 2 years.
It sounds to me as though your Mom's doctor is being quite realistic in saying that he really doesn't know how long your Mom has - I think the best thing that you can do in a situation like this is prepare for the worst, yet hope for the best. Doctors are under alot of pressure these days to be very forthcoming with patients, and for this reason will often include a 'worst-case scenario' picture (I remember my Mum telling me that when she was young, doctors often didn't even tell patients when they had cancer!).
This is a wondeful site for exchanging information, and giving/receiving support. I am so glad you found it.
I wish you and your family, especially Mom, the very best.
Karen