Hello Brian,
Welcome to alt.support.cancer  I'm sorry to hear about the circumstance that has
brought you to us.

Death is not predictable. We rarely know when or how it will happen. Even his
doctor will not know for sure exactly when he will die.  I could visualize a man
getting thinner and thinner (not eating), then suddenly being bedridden due to a
fracture and dying from heart failure or pneumonia (and I could be totally
wrong). Can you at least talk to his doctor to find out where the "mets" are, if
applicable ? And any other known health issues?

"Late in the course of stomach cancer, weight loss or a palpable mass may be
present. Finally, tumor spread or metastasis may lead to an enlarged liver,
jaundice, ascites, skin nodules, and fractures."
http://www.merck.com/mrkshared/mmanual/section3/chapter34/34b.jsp
(Ascites: a collection of serous fluid in the cavity of the abdomen).

If you're nearby, would you recognize signs of jaundice (yellowing of the whites
of the eyes and skin)?
But there's so many possible unpredictables like uncontrollable bleeding,
pneumonia or other overwhelming infections, other organ failure (heart/kidneys).

I realize there may be practical reasons for asking.  Like when to take time off
work? When to advise other family so they can see him one last time?  Or when to
go, if you are in a different place or when to involve palliative care (if
there's financial difficulties) or when to talk to them about same end of life
issues?

Stay with us, we'll help in any way we can.
J