Well guys dont take tension. It doesnt mean that every security clearance takes upto 6 or seven months. It depends upon the info you filed and your address etc.
For example if a person has two addresses i.e. Permanent & Current addresses are different it will take time. Moreover if a person has an address of a far away village it will take more time to verify such information. If a person is residing in a city with an easy and traceable address the time will be upto maximum four months.
The time span can also be calculated by the persons who contacted you for your security clearance. Number of agencies (upto 9 or 10) will be chasing you but only 3 or 4 will contact you. So keep in mind when 2 or 3 persons visits you for your security clearance it means that in upcoming month or so your security will be cleared.

Regards