[Ibrîniðilpathânezel]

The Valar cannot take away the "Gift of Men"; only Eru can, and as far as we know for certain, He may have done so for Tuor, and whether or not He did is never made clear. Earendil was literally half-Elven, and thus became the first person subject to the choice of the half-Elven, to be either of the mortal Men or immortal Elves; Elwing's blood was somewhat more mixed, having that of Elves, Men, and a Maia, but again, she was offered the choice. In his letters, Tolkien makes it very clear that Frodo would not have become immortal by going to Aman; he was being allowed what he called a "purgatorial" grace to spend the remainder of his life in the bliss of what was left of Arda Unmarred, so that he could find healing and peace before his death. At the moment, I don't remember precisely where he said it (I believe it was either in the Letters or in the HoME books), but it was believed that because of the presence of the Powers, a mortal in Aman would wither and die even more quickly, like a moth near a flame. So the erroneous belief that Sauron planted in the minds of the Numenoreans, that they could become immortal by seizing Aman, was a lie, designed to bring about their destruction, not grant them immortality. Which, I think, is very much in keeping with Sauron's personality.