Not just the age of the domain but also the expiration of the domain name will play a factor.
Google likes to see that someone has been around for a long time - that generally means authority on a subject. Also, if you have registered your domain name for many years out that will also give you a bonus as it shows that you're around to stay and not just testing the waters.
Just did a search on Google for web hosting providers and number 5 on page one shows their domain was created in April 2008 and expires in 2010. Have never done any real research to see what effect age has, but some swear it does and others don't. I have to believe it does play some role in their algorithms. Of the top seven, six had a longevity of at least four years.