For some unknown reasons people do believe that as a website gets older it gets higher rank on Google SE. Because of this belief people start believing that just because more number of users are using the site, it gets upper rank. While this is true but the reasoning behind this is not correct. If it was like that, then all the web admins would do nothing but keep refreshing the page all the time!
I wonder, why the believers of this theory are not confronted by the question "how do Google know that how many people are using my site?". Think about it.
The most essential thing is the content of the site and the number of people who are interested in reading/searching that content on Internet. What happens is, when you search for something on the web and find something of your interest, you will click on that link. Google records your all the clicks against the search term you entered. Now as more and more people search for that term and start clicking on your link, Google ranks your site higher, simply because you have the content which interests the users. Simple!
Now, Google has introduced the +1 function for each search. So when people search for a keyword and find your site interesting, people will do +1. Need I say that this would boost your SEO greatly? ... :)
So here is the rule. it really doesn't matter how old your site is. What matters is your content which would interest people. Smart way, isn't it?