Matt Cutts from google has hinted that domain age does indeed factor into ranking although it's just one of the many ranking factors that google looks at.
But just buying an aged domain won't increase the ranking of the website and content.
Google also takes into account the age of the content and when the content was first crawled.
I have a website that didn't start ranking for keywords and getting good search traffic until the website had been online for 5 years.
After that 5 years the website has shot up in google search results for some keywords.
So when you create a website and want to rank it in googles search engine and get traffic, remember that it can take up to 5 years before you really start seeing results.
After that time then you should be ranking for keywords sooner when you write new content.