Thanks… Sorry I mixed two things… Now i found the post where he told about 90 days.
The timing can be tricky. Once you get an invite you have 90 days to submit all police clearances. We needed three for India, Singapore and the US. By far US was the slowest the delay was documented on the FBI website and attributed to some kind of system upgrade work in progress.
So I think he meant once we get ITA we have 90 days to submit FBI clearance… so he meant we should get FBI clearance done as soon as possible when submitting the profile or just before submitting the profile to meet that 90 days deadline as FBI takes two months to give results…
But I thought 90 days older FBI clearance… my mistake 
Anyways now its clear that it has to be within last 6 months as you guys posted above…
and Now you have 48 hours results option… So i think we will be good to apply for it once we are in the week when we will submit our profile finally… Right?
Actually, We are still waiting for ielts and ECAs because of delayed efforts and dates.