Feel for you mate, it's a horrible situation to be in. Think it's one of those things that everyone knows is bad but until you actually end up in that situation you don't realise just how bad it is and how it takes over your life. Plus there seems to be zero support for family members, probably not surprising given they can barely manage to support the person who is actually battling the disease.
It's so hard to just carry on with life but you can't take months / years off work to deal with the situation so it just totally takes over your life. When my Dad was finally diagnosed and entered end of life care we were told 3 - 6 months, but that 6 months was very very optimistic. He's still here 3.5 years later and it's such a weird situation that you feel like you can't really talk to anyone about without sounding like a dick.
We basically processed him dying, had everything planned for the funeral etc but he's still here, except he's not really. I think I last saw him awake about 3 months ago, on that occasion he thought I was his brother, he's never had a brother, he thinks his Mum & Dad are still around, who would be about 120. On the one hand you feel you're totally wasting your time visiting him, even when he is awake he has no idea who you are and the second you leave can't recall that anyone has visited, but the other hand you look at so many people in there whose family only show up once or twice a year.
Its really made me question if we do the right thing in keeping people alive as long as possible. His doctor said to me a while ago that the problem is we've got to a stage where we're so good at treating things we're keeping people alive far past the point that their bodies and brains can cope with. Is there really any benefit having him lying in bed 24/7, confused and distressed when he is awake. Who benefits?