When did the last of the High Elves leave Middle Earth ?

[Inziladun]

Originally Posted by Galin

So again, what about The Lord of the Rings alone? Perhaps one can interpret the term to refer to the Exiles at all instances, but I don't see this as a given necessarily.

Well, going back to the Letter #144 quote, Tolkien, at least at that time, was apparently certain that the High Elves encountered in LOTR were Noldorin.
He refers to them as 'Exiles', and 'part of one of the last main kindreds of the Eldar: the Noldor.'