My husband was diagnosed 11 years ago, when he was 53 years old. Doctors really do not know about the length of the disease. He really lost his speech very quickly, But 4 years ago the worse problems arraised: agressive behavior, with medication the problem passed. You have to be strong and stand this stage, it will pass. Since 2 years ago he has become totally incapable of doing anything by himself, as eating or drinking, also he started to use diapers. Now he is loosing totally his capability of walking. What I have been told is that once the patient is totally postrated you have one year. He still lives at home and recognizes me and understand some basic things, they understand more things that we imagine.
Hope this helps you, try to enjoy your love one the most that you can.