[Dûrbelethwen]

I noticed many on this board think that those mortals who are allowed to go to Valinor die at the end of their usual life spans. I think that they become immortal. I am "reading" the Letters of JRR Tolkien (I put reading in quotes because it is rather difficult to read it in the usual sense).
In one of the letters Professor Tolkien clearly states that Tuor was given elf immortality just as Luthian was given human mortality.
Second is what Professor Tolkien says about Valinor in one of the letters: " But in this story it is supposed that there may be certain rare exception or accommodations (legitimately supposed? there always seems to be exceptions); and so certain 'mortals', who have played some great part in Elvish affairs, may pass with the Elves to Elvenhome. Thus Frodo (by the express gift of Arwen) and Bilbo, and eventually Sam (as adumbrated by Frodo); and as a unique exception Gimli the Dwarf, as friend of Legolas and 'servant' of Galadriel." All the inside quotes are the professor's.

Another point (though I admit a shaky one) is why would Bilbo and Sam sail to the Undying lands late in life if they were going to die soon anyway. Particularly Bilbo for I do not see a reason why he could have not died in Rivendell, I am sure the remaining Elves there would have given him a very nice funeral.

A final point is in the appendice the Tale of Aragorn and Arwen. At the end of his life Aragorn told Arwen to leave for the Undying Lands now that would soon be dead. It would be safe to assume this is because he wanted her to take back her immortality.