[Mithadan]

This is a question that cannot be answered with certainty. The was a discussion a few years ago in the Books forum that, at least, touched upon this, though the ultimate question was what did Tolkien decide regarding the source of the version of the Red Book that he ultimately "translated?" The thread was entitled Transmission Theory, and by no means am I suggesting that your question has already been discussed or should not be addressed here.

Certainly, Tol Eressea remained a component of his mythos until the end. Similarly, Pengolodh makes appearances late in Tolkien's philosophical musings. Aelfwine also appears in his writings at least as late as the 1950s. Some argue that Aelfwine (a favorite of mine) was no longer necessary after JRRT initially settled upon Bilbo/Frodo's Red Book as the source of his stories, and later questioned whether early mythology was from Numenor, explaining inconsistencies with science.