Why the govt increased tenure of Director, CBI?

Why did the government increase the tenure of the CBI Director? DoPT Minister Dr Jitendra Singh gave the reply in the Rajya Sabha while presenting the bill. According to him in several countries, the term of Director and Chief of a premier investigation agency is in the range of 6 to 10 years, and in the case of CBI, the tenure of Director is fixed as a minimum of 2 years but how much beyond it, is not defined. He said, with a view to make the Agency more democratised and institutionalised, the amendment to the existing Act has been brought. He said, after two years the tenure of Director of CBI will be extended for one year at a time. The Union Minister said that the Modi government wants to make the law more candid and clear. Later the house cleared the bill. Lok Sabha had already passed the bill.  Hope this will clear the clouds of suspicion.