: : Hence I reject the original statement.

: Actually I think that's one of the srongest themes: Labor and trials and good deeds done. the heroes (some anyway) retire to the land beyond the sea, presumably to live forever in bliss.

Well, I would suggest that as Tolkein is prtraying Middle Earth as the history (or an alternative history anyway) of our own world, there is mo question of Christianity in it - Christ after all had not been born yet. The book is strong with good against Evil suggestions, and the elves get to go to Valinor, which is part of Ea (existence), but Illuvatar has a special fate for Men, that they pass outside of Ea when they die, and share his existence, Heaven if you want to call it that.
Morgoth was banished to the void - the nothingness outside the walls of night, this if you like is Hell, but not in the Christian sense of the word.
In sort, IMHO, Christianity is incompatible as it did not exist at the time this was written.
Dave