Its good business sense to register a domain for at least 10 years.  You don’t want to deal with the process   annual process of renewing them every year. It’s best to obtain the domain names that you want to keep for a while and renew then on a 5 to 10 year plan. It is beneficial for search engine rankings as well to  register for more then one year, you seem more serious to the search engines if you do.

If your domain name expires, there’s a good chance that someone will register your domain name immediately after it expires.  If,  for whatever reason, you don’t renew your domain name, someone watching a ‘watch list’ of expiring domain names will try to capitalize on the online business that you’ve built over the years.

They know that there is potential website traffic they can have simply by renewing your old domain name. By renewing your domain name for several years, your domain name won’t expire for a while, and it won’t be opened up to expired domain name buyers.