pageoneresults - 11:04 pm on Nov 22, 2011 (gmt 0)
I'd say lexipixel summed that up real well. :)
From the moment we discover a new article, we'll keep re-crawling it looking for changes. Since we've noticed that most changes to articles occur just after they're published, we revisit articles most frequently in the first day after we've found them. After that, we visit them less often.