[CSteefel]

The other perhaps minor point is that Gollum says he was captured on the "cold hard roads" to the East of the Dead Marshes. But one would think that once he learned the passage of the Dead Marshes, he would have only used that path to and from Mordor (as he did when he left Mordor in 3017). In other words, the use of those cold hard roads would have been more likely to be an early mistake, which again implies that perhaps Gollum was captured on one of his earlier visits.

Arguing most strongly against this is the material in The Hunt for the Ring (which agrees with the accounts from The Council of Elrond) that Sauron learned what Gollum knew only in 3017.