Google's patent application 20050071741 displays how they rank sites on historical data.  Meaning that they pay attention to when your domain was registered and how long it's been registered for.  Older domains have an advantage in Google's serps over newer domains.  If you have a domain name and plan to be around for awhile then it's good to register your domain for longer then the 1 year minimum.  I'd say register your domains for atleast 3 years in advance just to let Google know you are serious and plan to be around for awhile.  Most spam sites are only registered for 1 year then let expire so it's good to set yourself apart from these domains by extending your registration.
Here is the Google Patent in full.  You will see #'s 38-40 pertain to a domains information.
38. The method of claim 1, wherein the one or more types of history data includes domain-related information corresponding to domains associated with documents; and wherein the generating a score includes: analyzing domain-related information corresponding to a domain associated with the document over time, and scoring the document based, at least in part, on a result of the analyzing.

39. The method of claim 38, wherein the scoring the document includes: determining whether the domain associated with the document is legitimate, and scoring the document based, at least in part, on whether the domain associated with the document is legitimate.

40. The method of claim 38, wherein the domain-related information is related to at least one of an expiration date of the domain, a domain name server record associated with the domain, and a name server associated with the domain.

An overview of the importance of domain age can be found in this article at webconfs.com.  I just extended jeffhendricksondesign.com until 2010.