I would think that age would play a minor part in a sites ranking but that the algo would not rely to heavily on it.

If you think about it there are thousands - no, Millions of sites out there that are simply spammy and created for the sole purpose of promoting a main site.

If a site is old, say 8 years, chances are its legit, and not simply a doorway.

Also, for sites that have been around since the early days, its likely a safe bet that they do hold some level of authority on the topic.

- Really when it comes down to it, I doubt there is much weight on this at all, but I would not be surprised if there was at least some.