Big Tom, I read your post earlier today, but couldn't bring myself to respond then. I feel a little stronger tonight. I'm going through a similar thing with my dad (my mom passed 2 years ago with the same horrible disease). They disappear before your very eyes and leave this other person that's just a shell of the real "dad or mom, or sister, or brother". But as hard as it is, I wouldn't trade this opportunity to be with him for anything. And knowing what's at the end, there still isn't any way to prepare for it. I feel for you, and the truth is he'll never really be gone - you'll carry him with you every day from here on out. My pillion pegs are still down for my mom, guess they'll have to share them when he goes.
Take care of yourself and any siblings, and know you got all of us.
--Dave