[Mithalwen]

All I would add is that it symbolically raises Merry and Pippin to be on a par with Aragorn. They have not the "gift" of the Numenorean kings to give up their lives at will but these two holders of the great hereditary offices in the Shire choose the moment to pass their offices and estates on. It is not forced on them by failing health or death. Effectively they did to their families and friends at the moment they leave the Shire and although they may not pass over sea like Frodo, Sam and Bilbo, they spend a time in places where they receive honour and perhaps have a chance to reflect on the extra-ordinary events that tempered their lives.

Although the religious aspects of the Lord of the Rings are not something that impinge on my general readings of the book (they are not unavoidable as in Pullman or Lewis), the idea of making "a good death" is a very Catholic one and seeing their departure to Rohan and Gondor as a time of retreat and preparation (if not an actual Purgatory) does make it seem less unnatural. Within the internal religion of Ea, choosing death (even symbolically) at an appropriate moment identifies Death clearly as the "Gift of Illuvatar" to mortals, not the doom or curse that lesser or fallen mortals perceived it to be. So although on a human level, it seems "wrong" that the hobbits voluntarily choose to leave their families, symbolically Tolkien raises them to a high level both spiritually and temporally.

I think it is nice that having been born to be big fish in a small pond, at the end they are honoured for the things they acheived for themselves. They have been returned to the wider world and there their high status are due to their deeds not their birth.