Does any know how long the Name check clearance is valid? Is there any rule for NC also like FP valid for 15 months? Does USCIS request 2nd time name check if needed?
FBI NC clearance is typically valid for the duration of that I-485's life. So it doesn't expire like FPs do. Rarely, USCIS ends up asking for an FBI NC more than once. As long as the latest NC request is cleared, it should not be a blocking factor.
Depending on whom you speak to, it could be valid for as less as 24 hours. eg: I call today and will be told it is cleared, tomorrow it is not cleared...