I went to a talk that swedish crime novelist Leif GW Persson gave a few years back. He started talking about how his books have gotten longer since he started writing back in the seventies.

He said that back the he wrote on a typewriter and it was a pain in the ass to go back and change stuff and the very act of typing and changing papers limited the length of the book.. When he started using a word processor he could just let the text run on and on.

I think he has a point.