Basically, he will have to look at visa number in hand( A) and applications that a ready to be approved (B) and decide how far he can move the dates. B will not include all incoming applications, just the ones that could consume visa. As 'A' dwindles, his ability(reason) to move dates farther goes down. yes, date-movement is to build pipeline, but also must meet the legal-framework as much as possible to avoid ruckus.