This is such a great glimpse of Elros--and of Elrond, and of their relationship. I especially like the ending, harkening forward to Aragorn's last words.

I love the thoughts you've put into Elros' head. His determination not to look back, his sadness at missing his brother even though he is excited to sail the sea (running in the family, one presumes), his observation that Gil-galad has good reasons to keep Elrond by his side, and finally his decision to make his new country so beautiful that Elrond can't resist visiting - it all rings very true. And his final observation about journeys into the unknown is a chilling reminder of just what his choice entails.

"How far I'll go" certainly fits Elros perfectly and you show it to us--all the way to Numenor and beyond the Circles of the World!

I think you've said a lot in here; despite your own comments, it doesn't feel "short", if you know what I mean.