Our capacity for artificially extending life seems to be growing by the day. If you don't let your family know what you want, undoubtedly they will do everything in their power to keep you alive. Even if it means feeding you through a tube surgically implanted into your stomach and inserting catheters and tubes into places that were designed to be "Exit Only".
If this is how you want to spend the last few years of your life, please, have at it. However, if the thought of laying in bed in the same position until someone can turn you, having someone clean you up after you soiled yourself and watching your roommate eat while they put fluids with vitamins in them directly into your stomach through a tube, please fill out a Living Will and any Advanced Directives before you think you should. If you wait until you become injured and/or sick, you may not be able to tell your family to let you go quietly. They may decide that you like living in this condition or that you will be "up and dancing in no time" if you can just get over this bump in the road.
I am all for hope. I believe in miracles because I have seen them. But my residents who have been on a downward spiral for several years deserve to be put under hospice care and allowed to meet their Maker with dignity. A little preparation in advance of catastrophe would allow them to do that instead of being forced to exist just because their families don't want to let them go.