Why Does a Domain's Registration Length Matter for SEO?
When it comes to using a domain's registration length as an SEO factor, the premise is that a more committed website is more likely to stay in business and devote a greater amount of resources towards developing a high quality source of information. Terms like "Going Concern" and "Declaration of Intent" are used in the business world to establish a long term commitment. Serious business will always implement this concept, that they intend to be in business for the long term.
This is obviously a gross generalization and can be argued against on any terms. Certainly not all great websites have extended registration lengths and certainly a low quality website could potentially have a very extended registration length. However, upon analyzing a database of websites, a correlation begins to emerge. Major websites, which typically do well in search engines tend to have longer registration lengths than small start-ups and low quality sites. There are probably a number of good reasons for this correlation. Does this merit the potential use of registration length as an SEO factor? Additionally, Google's patent states that this metric could be used as a signal (in conjunction with other signals) that a particular site may be more likely to be spammy if the registration length is very short.
Arguments Against the Use of Domain Expiration
This metric is not a very reliable piece of information to use to distinguish reliability of one site over another. Many sites, regardless of quality, have automatic renewals set so that their domain never expires unless the webmaster manually disables the auto-renew feature. This lends to reason that high quality sites can be deceptively near their "expiration date" even though auto-renew is set to occur for another 5 or 10 years. Whether or not search engines have access to this information is unknown to me (If anyone DOES know, please advise). So for the sake of justifying the use of this metric and not to underestimate the search engines, I am going to assume that the true expiration date of a domain is the current length of time left till the auto-renew PLUS the length of the auto-renew. It's still by no means an accurate measure, but there is an important point to be made...
Statistically speaking, since there is a correlation between "successful websites" and the length of their registration, it is a metric that can be used to grade the reliability of a site, it will just be a very very small factor. But, a factor nonetheless.
Varying Opinions on the Use of Registration Length.
Many popular SEOs have disregarded the application of this metric as a real ranking factor. In some sense, they have a good reason to dismiss it since it is a weak metric to analyze, but as long as a correlation exists between the registration length and the long term success of a website, it should be considered. In the end, this metric may hardly have any effect at all, but the idea behind having an effective algorithm is that it consists of many many small variables that can not be gamed and do not individually have too large of an impact that certain sites will inherently have a disadvantage at all times. By diversifying the range of ranking parameters, we can expect to have a more comprehensive analysis of a website even if some components hardly make a difference.
"...ignoring the time remaining before a site expires can coincide with ranking decreases because its often a symptom of poor management or ignoring a site altogether." - Fahrenheitmarking
Even though the source of the previous quote disagrees with the use of this metric as an SEO factor, their statement illustrates my point exactly. To some degree, a site very close to its expiration date is more likely mismanaged, making it a lower quality site.
"...and scoring the document based, at least in part, on whether the domain associated with the document is legitimate... wherein the domain-related information is related to at least one of an expiration date of the domain, a domain name server record associated with the domain, or a name server associated with the domain." -Google's Patent
|Yes, it matters.||No, it doesn't matter.|
Matt Cutts ("Wouldn't worry too much")
Registration Length Ranking Function
Assuming the registration length and renewal dates can be extracted from a site, this variable can be plugged into a ranking function and scaled in a relatively reliable way so that it does not help or hurt a site unfairly in either direction. This will be a small scale factor and so the difference in grade between 2 sites will be rather minute even if there is a somewhat large difference in the variable itself.
F(x) = [ln(x)]/[1-(x/100)]
Where: X is equal to...
Where x is equal to the expiration date minus the current date, plus the length of the auto-renewal time period.
Best Practices and Optimization Tips
Register your domain for as long as you can. Matt Cutts himself stated he often renews his domain name for 2-3 years at a time, implying that was a pretty lengthy renewal. Many hosting providers like GoDaddy will reimburse you if you cancel your hosting or registration earlier than initially signed up for, so there is little risk in extending your registration lengths.
Avoid minimum registration lengths. If you are not in it for the long run you can not expect to make considerable boosts in rankings anyway. Remember the concept of "Going Concern".
If I register my domain for 5 years and have it set for auto-renew, should I worry about the affect on SEO as it gets near the renew date, which may make it look like it expires soon?
No, this is not something to worry about. Generally, an auto-renew setting is detectable if the registration information is also detectable. A site's WhoIs information should be able to provide this information. Don't worry about manually renewing your domain name every year just to make it look like it's always registered for a really long time.