I don't see that passage as grim. It acknowledges that absolutely nothing
in the Universe lasts forever, but isn't that a good thing really? I kind
of like the idea that the atoms and molecules that make up my body were once so
much primaevil sludge, and that long after I'm dead they will again revert to
that state - they are part of the eternal wheel that binds us all. I
think that what Tolkien is saying here is that Arwen was such a beautiful,
perfect being that her memory will be preserved until the end of conceivable
time - and yet even she was just part of that endless cycle that is life.
I think that Gandlaf would call that "a comforting
thought".
************************************
"What are you doing, Dave?"
