There are a lot of topics and posts out there regarding the age of your domain and how it factors into ranking better. Some believe that if you purchase or renew your domain for 2 to 3 years or more that it will give you some kind of boost in rankings.
Some people believe this to be the case. Others say it is a gimmick that domain registers came up with to increase sales.
Even some tools like websitegrader.com will through this warning message at you if your site is going to expire in less than a year:
The domain for this website is set to expire in less than a year (April 21, 2011 ).
We would suggest renewing this domain with your registrar. Google and other search engines may penalize websites with domains that are set to expire soon. The reason for this is that many spam sites are often registered for short periods of time. Most registrars support paying upfront for several years and the cost is usually only about $10-$20 per year, so it is generally worth it.
However, if you take a look at what Matt Cutts from Google has to say about this, you will see that Google is not too concerned with the age of your domain or when it is due to expire. He tells you not to worry about this much, not very much at all in fact.
Although he doesn't say that there is absolutely no weight or value for how many years your domain is registered for. He does say: "Make great content and don't worry nearly as much about how many years your domain is registered for."
Which seems to imply that if Google does put any weight or value on this at all, it is an extremely small amount. It really wouldn't be helpful to register your domain name for an extended amount of time where rankings are concerned.
If you have the extra cash to spend, and don't want to worry about registering your domain every year or two. Then, by all means pay it up for 5 or 10 years if you want. Just make sure that you intend to do something with it for that amount of time. It would be kind of a waste to pay up 10 years in advance for a domain name that you lose interest in.
Bottom line is that registering your domain for 2 or more years will not give you a significant bump or boost in Google rankings. Based on this video very little or almost none in fact.