The age of a domain name can add significant SEO value to your website. The age of a domain can indicate a certain level of trust and even authority with the search engines. This generally means that search engines will display older websites with established trust and authority, before brand new websites.
The Sandbox
Many speculate weather Google has what is referred to as the “sandbox effect,” which temporarily reduces the PageRank for new domains to prevent manipulation from optimizers; i.e. making it more difficult for new websites to rank well in the search results. Speculators say that the “sandbox effect” could last as long as 12 months.
There is also thought to be a “reverse sandbox effect,” where new websites without any inbound links would get a temporary increase in PageRank, sort of like a “New Release” to help give the new site more attention temporarily.
Buying a Used Domain
If you are thinking of buying a domain that has been around for many years as a way to thwart this so-called “sandbox effect,” you can expect to see a drop in PageRank while Google figures out how the new site compares to the old site for this domain.
If the new website has generally the same content and relevancy, the PageRank should go back to where it was and keep the link juice from all of the existing inbound links.
However, if the new site is NOT the same content (i.e. went from a jewelry site to a real estate site), the PageRank drop may be permanent, and it would be similar to starting with a brand new domain, and hence the “age” of the domain will essentially start over in the eyes of a search engine.