[William Cloud Hicklin]

It's perhaps worth observing that Tolkien was in the habit of expressing himself, for brevity, in an elliptical form which appeared more definitive on the surface than his actual intent; this is especially true of his frequernt use of 'rhetorical hyperbole' ias in "fairest," "greatest," "Eldest" etc. Given that this is Tolkien, again writing in compressed form (and the appendices as published were decidely 'comprerssed' from his point of view!), "depart with him [Elrond]" doesn't I think necessarily mean that they had to get on the same boat. Would it "count" if they sailed on another ship in the same flotilla? One that weighed anchor a day later? A week? And if that, then why not within the same 'yen' (144 solar years)? In the Elvish view of time, that's practically the next day.

(Incidentally my own inclination, given the Twins' fierce attachment to their mother, is that they did sail West to be with her again).