Yep. They've got all day and night to watch and learn the movements, habits, and how things run. If you have the same routine, the same schedule everyday, and you do the same thing at the same time every day, those employees involved in illegal activities can develop their plans of action to take advantage of this. They'll recognize your short-comings, and use it. They'll know what area they can conduct their illegal activities in, and when the best time is to do it. One of the things I learned from working in Corrections for 25 years is to not get in the habit of doing the same thing, at the same time each day. Don't be predictable. If at all possible, change up your routine to keep them guessing.
Even then, it seems such a charade, with so many loopholes.
Islamoterrorists bent on suicide seem to not want to chance getting caught, which they might be at the last second by vigilant passengers even if they completely fool screening. And if they do, there goes their guaranteed free ride by glorious suicide attack to a virgin filled heaven. (I believe all such caught attempted terrorists should NOT be put to death, starving the cause of a martyrdom.)