What Is The Life Expectancy In Case Of Alzheimer's Disease?

Hi, I am Elena. my father suffered a massive stroke 8 months ago today and is his 66. he liked to keep fit and lived a healthy life always. Never smoked, never at meat however had high bp, cholesterol, beat benign lung cancer 14 years ago and was 4 years in remission from prostate cancer. 1 year before the stroke he had a triple bypass and now he is in a care-home, with no swallow, peg fed, paralyzed on the right side (arm & leg), and not able to follow basic command like squeeze my hand, look at the watch - we don't think he even knows who we are anymore as he'd stage 2 Alzheimer. I would like to know what his life expectancy is going to be - he would have preferred himself to be dead if he knew his condition and in a way, we have come to feel that it would be best given that he isn't recovering plus he is showing signs of bed sores and chest infections.