Impact on SEO - domain name years?

Hi.
I want to ask what is the real impact of your domain age and domain expiration. It turns out if you buy your domain for 3+ years it is good for SEO. What is the impact ?

Thanks

I have believed this for a long time too, until I figured out that I could rank a brand new domain even better by pointing just an old domain to the new one!

In regards to buy the domain for 3+ years again I heard the same but can't remember anyone yet to prove that to make any difference in ranking. Hope some can do so since it's interesting questions.