Oooh, sorry about that. I remember reading something like that once. But I just found out that it was not 1000 years, but 400 years. Still, compared to Jesus, who was first written about when plently of people who knew him were still alive, that says something.
Of course, there could have been manuscripts about Alexander from eariler that were destroyed, but who knows.
From what I've heard, the main reason the Gospels were written in the first place was that the Apostles were dying off, distortions were creeping in, and the end of the world wasn't coming as quickly as they'd assumed.