[akhtene]

I've always believed that the main implication of the Choice was not where or how long the half-elven were to live, but where their fea went after death. Mortals didn't stay at Mandos forever, like elves, so Arwen decided to follow Aragorn wherever he went, beyond the limits of Arda.
And by leaving M-E with Elrond or remaining there Elrond's children just declared what choice they have made.