Region: Middle Earth
March of Maedhros offered a nice short but thorough answer. The island and the history behind it is explained in more detail in other Tolkien's books, especially in The Silmarillion. If you feel that you'd like to know more, or are still unsure, feel free to reply! Until then, I do have some questions to add to the conversation ...
This is interesting. Never thought about it like that, ie, they carry bits of the "evil" of Sauron with them so they must depart to the undying lands / Valinor so that Middle Earth is cleansed.
Can you, or someone else, evolve a bit more on this? Why Middle Earth was unsafe for the ringbearers, especially after the events after Mount Doom?
Except "getting a free pass" because they did valiant actions regarding the demise of Sauron / destruction of the One Ring and so they were deemed "worthy" to board the ship for Valinor.
Are you referring to the Hobbits departing for Valinor with the above quote? Ie, They had to "leave" because it was impossible morally / spiritually for them to remain in Middle Earth because they suffered great emotional and psychological toil that messed up their perception and enjoyment of life in The Shire?