Immortal languages again

A recent thread got me wondering how the language of a species that was
truly immortal would evolve. I came up with the following idea.

Suppose we have a species that's completely immortal, and therefore doesn't
need to reproduce. However, they're still material beings and there memory
is fallible. Let's say, for the sake of argument, that the half-life of a
bit in their memory is about a thousand years. In the mental representation
of a word, a bit might represent the presence or absence of a distinctive
feature. Each time they hear a word in conversation, two processes occur-
1) They adjust their mental representation of the word towards what they
heard, in order to correct for inaccuracies in their pronunciation.
2) The likelihood of them using that word themselves increases slightly.

Some words will end up being used far more frequently than others. The
pronunciation of the most common words will on average be corrected more
quickly than it drifts, and hence the consensus pronunciation will remain
fairly stable over time. However, for less common words, the rate of drift
will be similar to or exceed the rate of correction, thus leading to the
pronunciation varying significantly over time. In some instances, by the
time somebody hears a word again, their mental model of it may have
diverged from the speaker's mental model so much that they no longer
recognise it as the same word, thus leading to the creation of a new
vocabulary item.

Pete