'And when they came into the West the Gnomes for the most part inhabited the Lonely Isle, that looks both West and East; and that land became very fair, and so remains. But some returned even to Valinor, as all were free to do who willed; and there the Gnomes were admitted again to the love of Manwe and the pardon of the Valar; and the Teleri forgave their ancient grief, and the curse was laid to rest.' Quenta Silmarillion, § 27 The Lost Road
That was the version written before
The Lord of the Rings (and according to
The War of the Jewels Tolkien made no cursory correction to this section -- though see Christopher Tolkien's commentary on this). However, 'probably' late in
1951 Tolkien wrote a letter to Milton Waldman, explaining:
'We learn that the Exiled Elves were, if not commanded, at least sternly counseled to return into the West, and there be at peace. They were not to dwell permanently in Valinor again, but in the Lonely Isle of Eressea within sight of the Blessed Realm.'
In
1954 in a letter to Naomi Mitchison:
'But the promise made to the Eldar (the High Elves -- not to other varieties, they had long before made their irrevocable choice, preferring Middle-earth to paradise) for their sufferings in the struggle with the prime Dark Lord had still to be fulfilled: that they should always be able to leave Middle-earth, if they wished, and pass over Sea to the True West, by the Straight Road, and so come to Eressea -- but so pass out of time and history, never to return.'
In Author's note 4 on the Commentary to the Athrabeth (itself thought to be dated around
1959 by CJRT):
'The passing 'oversea' to Eressea (an Isle within sight of Aman) was permitted to, and indeed urged upon, all Elves remaining in Middle-earth after the downfall of Morgoth in Angband.' In August
1967, in drafts for a letter to Mr. Rang Tolkien refers to the ban on Aman of the Exiled Noldor, but that the Exiles were allowed to return except a few chief actors in the rebellion (Galadriel), and in a footnote notes that Galadriel wished that Frodo may be granted a sojourn in Eressea, an Isle in sight of Aman.
In
1971 Tolkien writes to Roger Lancelyn Green and seems to use
Aman as if including Tol Eressea, and says Frodo or other mortals could only dwell in Aman for a limited time:
'The 'immortals' who were permitted to leave Middle-earth and seek Aman -- the undying lands of Valinor and Eressea, and Island assigned to the Eldar -- set sail in ships specially made and hallowed for this voyage,...'
We know that the Silvan Elves sailed over Sea according to
The Lord of the Rings. In a text dating
'1969 or later' Amroth says to Nimrodel:
'It is said that the grace that the Valar gave to us to pass over the Sea is granted also now to any of those who made the Great Journey, even if they did not come in ages past to the shores and have not yet beheld the Blessed Land.' Amroth is of Sindarin descent, thus Eldarin. Nimrodel was a Silvan Elf who regretted the incoming of the Elves from the West (West-elves or Eldar) but is still allowed to pass OverSea.
From this much at least, I think that the Sindar and the Silvan Elves could sail to Tol Eressea or lands West. It would seem that the Exiled Noldor were supposed to reside in Eressea, at least 'permanently' anyway (suggesting they might visit lands West), according to the letter to Waldman in 1951 (and also noting that upon death it seems possible to live again in lands West of Eressea). As an interesting comparison to the version of Quenta Silmarillion quoted above, I note the constructed Silmarillion here:
'And when they came into the West the Elves of Beleriand dwelt upon Tol Eressea, the Lonely Isle, that looks both west and east; whence they might come even to Valinor. They were admitted again to the love of Manwe and the pardon of the Valar; and the Teleri forgave their ancient grief, and the curse was laid to rest.'
These citations are not exhaustive however (and are not meant to be) so if anyone has texts or opinions to add, please do!