How long can an elderly person live without eating?!

How long can an elderly person live without eating?

my grandmother has pulmonary fibrosis, renal failure, she has lost 40 pounds in a few short months. Now she will not eat, maybe a cracker here and there and a few sips of water. I just was wondering if anyone has been through this, and what or how long to expect.

My maternal grandma {may she rest in peace} went into a deep depression when she had a cerebrovascular infarction and became bedridden. Until then, she'd been an active, self-sufficient woman: had her own car and drove wherever she needed and took care of her house; she'd been on her own since age 28 {my grandpa divorced her to marry a 16 y/o girl, and she had to work to support her two small children}. Seeing herself in a situation where she could no longer take care of her own most elemental needs, she told my mom and me the following: "Living like this isn't worth the effort, I don't want to keep on living like this; please let me die". Those were the last words she spoke; she closed her eyes, and closed her mouth; we tried to give her liquids but there was no way she would take them. The only time she opened her eyes again was to fight the doctor and me when we tried to insert a feeding tube. We decided not to insert the tube; she lived for 12 days w/o receiving any food or water. I know, she starved to death; but it was on her own free will, and we complied with her wishes to be left alone and not force-feed her. If we had done otherwise, the only thing that would've been accomplished was to prolong her pain and suffering. Its my belief that the important thing is QUALITY of life, not quantity. By the way, I've got a living will; this is a legal document in which I give instructions that my life not be prolonged by any artificials means if some day I get into a similar situation, and that medications to relieve pain and suffering be generously administered to my person even if they have the effect of shortening my life.