I have no proof to back this up (of course, what proof is there about anything regarding Google?), but I've noticed that new pages on an established large site seem to rank well more quickly.
I've seen this lately with one of my large sites. It's an authority site in it's niche and now I'm seeing new content pages on the first page of results within days. Usually around a week. Mind you these are specific keyword searches and low volume. But still, the new unique specific content page is ranking in days... very nice, I'm getting record traffic from the SE's now (over 50% of all my traffic is from SE's).
IMHO, as long as the content is unique and valuable then more content does boost rankings. It does seem that authority sites get more of a boost than non-authority sites. But then again, we're all aware that there are plenty of things the big G considers when giving PageRank and ranking pages, so who really knows :)