John Mueller confirmed that Domain Registration Length Not an SEO Factor.
So, if you are worried about it, then relax. Domain registration length will not help you in SEO.
Domain registration length was a ranking factor, earlier than 2009. But later Google stopped using it as ranking signal. I found a popular discussion on Google webmaster forum, where John Mueller responds to the same question, in 2009.
A bunch of TLDs do not publish expiration dates — how could we compare domains with expiration dates to domains without that information? It seems that would be hard, and likely not worth the trouble. Even when we do have that data, what would it tell us when comparing sites that are otherwise equivalent? A year (the minimum duration, as far as I know) is long in internet time.
Now again, in 2016, this is still a myth. Still, Domain registrar uses this as a sales trick to sell domains. Someone asked this question to John. John replied.
AFAIK most registrars don’t provide registration length anyway. That’s not what you want to spend your “SEO time” on. Here is the tweet by John.
@bill_slawski AFAIK most registrars don’t provide registration length anyway. That’s not what you want to spend your “SEO time” on.
— John Mueller (@JohnMu) November 3, 2016
So, next time you renew your domain, don’t think too much about the Domain registration length. Focus on SEO.