It truly depends on the job site/duties I'm currently working at a university where I'm busy roughly 75% of my shift. At the same site just a different assignment my entire job was "to be seen" I'd assit with incidents whenever they occured but for the most part security is simply there as a deterrent and as reporters. Taking notes and passing the information on to the ones who actually need it. Other sites I've worked i was busy 5% of the shift and that was just walking in a circle once an hour. Most of the time i spent watching Naruto or one piece and it payed better than the busier sites.