In a False Claims Act suit, a time factor is material where the governing statute references a regulation that, in the process of defining the list of terms within the referenced regulation, subsequently incorporates the timing factor.
Past practice is not dispositive at the motion-to-dismiss stage where there is no showing that the government was aware of the factor.
Training and instruction publications can help to establish that a certain factor goes to the essence of the bargain.
Sufficient proof of scienter for trial where deft instructed cursory review, was advised of requirements, and implicitly referenced the violation in internal emails.
http://www.opn.ca6.uscourts.gov/opinions.pdf/18a0110p-06.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.