This is just like thriller Bill in the 90's wit his definition of "is".
I bet it's daily.
Here is the article.
“Does the FBI use drones for surveillance on US soil?” Sen. Chuck Grassley (R-Iowa) asked Mr. Mueller during an oversight hearing on Capitol Hill Wednesday before the Senate Judiciary Committee.
“Yes,” Mueller responded bluntly, adding that the FBI’s operation of drones is “very seldom.”