My husband is 76 and has had Vascular Dementia since his late sixties. He is now basically bed bound, doubly incontinent, sleeps most of the time and has very few moments of lucidity. He eats small blended meals sometimes, more than others. While mostly a placid gentle man he has moments of extreme agitation and becomes very uncooperative if nurses are trying to help him. What kind of life expectancy is there I this stage of the illness?