Given what we know about the biology, the guideline that pest professionals generally accept goes like this. Wait at least 3 to 4 weeks after the final treatment, and during that time keep a careful watch for live bugs, bites, fecal spots, shed skins, or any other new activity. If nothing at all has appeared in that window, it is reasonable to conclude the infestation has been eradicated, and by 60 days the truth is clear one way or the other.
Virginia’s state pest control guidance, among others, suggests follow-up inspections spaced 2 weeks apart, which allows for egg hatch and for any stragglers that survived the first pass. (VDACS)
So when a warranty runs longer than 60 days and still promises “complete eradication” or “no reoccurrence,” it is fair to wonder what exactly is being sold, because the biology stopped supporting the promise a month earlier. Mostly, what is being sold is reassurance.