Sam's final journey

[mhagain]

You are quite correct re: Sam, but I personally (others may differ) wouldn't consider Letters as being in any way "canonical", but rather containing condensed explanations of JRRTs conceptions of the way things are at the time the letter was written. As we all know, he did change his viewpoint (often quite radically) on a regular basis, particularly in later years, and particularly with regard to some of the more "core" features of his mythos.

I think the Avari element came from Laws and Customs. But they were also subject to "death" (in the form of bodily destruction), and would be summoned to Mandos. They could refuse (it was unlawful for the Valar/Maiar to compel the spirit of any of the Children in any way), and a substantial number of them did.