"Now Elros and Elrond his brother were descended from the Three Houses of the Edain, but in part also both from the Eldar and the Maiar; for Idril of Gondolin and Luthien daughter of Melian were their foremothers. The Valar indeed may not withdraw the gift of death, which comes to Men from Iluvatar, but in the matter of the Half-elven Iluvatar gave to them the judgment; and they judged that to the sons of Earendil should be given the choice of their own destiny. And Elrond chose to remain of the Firstborn, and to him the life of the Firstborn was granted. But to Elros, who chose to be a king of Men, still a great span of years was allotted, many times that of the Men of Middle-earth; and all his line, the kings and lords of the royal house, had long life even according to the measure of the Numenoreans."
It's very clear that the blood is responsible for his lifespan and to that of his line, which includes the Dunedain. Eonwe give a small increase to the common(if any were common) Numenoreans, but the line of Elros had much more due to the special mix of blood.