If you want to understand about how much a domains age affects its ranking then the best person to learn from is Matt Cutts. Matt is Head of Google’s Webspam Team and in this video he explains about registering domains for many years to assist in Google Rankings.

If you listen to what Matt has said here you can help to optimise your website yourself in terms of content and have a more success than worrying about the age.

This page was Google Webmaster Help – How much does a domains age affect its ranking