Google rewards longer registration periods as a sign of quality: Longer period of registration escalates the quality and reliability of the company. Registering the domain for a longer period ensures the existence and continuity of the company’s operations in the future.
When the companies make a long term investment in their products and services, it means they are more committed in their approach. They are interested in carrying their business forward and shall not change their domain abruptly if something goes wrong. Such a commitment increases the credibility of the company in the long run. They rule out the possibility of being a spam website which shall go on for a short period of time and close down when something goes wrong.
Thus, registration of domain for a period of 10 years with the belief that the business shall sustain for a long time is considered very promising for the search engines. This shall not only reduce the cost but also increase the traffic to the websites.