Someday, Sam would be gone and he wanted to make sure Dean had a family to keep him sane.
Noooo! Sam! Don't be gone!

I'm totally with Dean on this one. Sam needs to be some kind of immortal. On the other hand, I also like the little Winchesters/Immortal Uncle Dean angle. It's bittersweet, but it's good. Now I don't know what I want you to write/have written.

And Awwww! Duncan's training reminds Dean of his Daddy! I like that too.