fox mulder | sam winchester
To be fair, I've been 'updated' on my future through watching my show. It's not the same thing as actually remembering it happen inside my head, but sometimes I find myself talking about future things as though they've already happened. So if you count that, I'm mentally about four and a half years ahead of where I originally came from and about three and a half years ahead of him.
My theory about his update was that he got it because a version of Lucifer had arrived (I don't know if you ever met or talked to the angel Xaphania before she left?), and he didn't know much of anything about our world's version until he got the memories of it in the dream. So in a way, your theory does hold true, because it gave him the information I needed him to know at the time. Is there anything particularly missing in those six months, or did your dream basically include all the important stuff?