[CSteefel]

I agree that Gollum took his own sweet (or bitter?) time getting to Mordor, but I imagine this is a case a bit like the Taming of Smeagol, but with that extra element of fear instilled by Sauron, that Gollum really does not want to go there and resists as a result, but he is drawn inexorably there in the end. The competing wills there may explain the long time frames...

But the text says he makes two separate visits to Mordor and is released in 3017. He is captured by Aragorn, turned over to the Elves, then escapes and heads westward (not eastward), trying to cross through the Misty Mountains via Moria. Once there, he finds himself trapped (this is discussed in The Hunt for the Ring as well).

Apparently Tolkien felt there were some inconsistencies as well, which is why he mentions that Gollum really does not even know where the Shire is when he discusses this topic in The Hunt for the Ring.