I have been thinking that when blogs first get started and build their traffic and audience, they don’t get many comments. This makes me think about whether or not blog readers go to the old posts and comment on them after the blog gets big.
As a marketer, I do this sort of thing. You have to keep in mind that the oldest blog posts have been indexed by Google for a long time now. This means that there is a good chance that those posts will get good pagerank on the next update. With that blogs success, you can actually receive some traffic and pr by commenting on old blog posts.
I find myself often browsing to the oldest post for other reasons though. One of those reasons is that in the beginning of the blog, the owner was more hungry for success. Chances are that their oldest posts were the most extensive and well researched of the lot. I have found some excellent posts by browsing to the first page of the archives.