Just my thought...

Would it be possible like, every Monday, the IO goes to the Workload Distribution Center (filing center) to get a box of files to work on for the whole week? This box has certain amount of cases and usually enough for the IO to work for the whole week. So as a government employee, the IO just take his/her time to finish the box and then can relax. Using this way, they can track down how much of the workload and the supervisor can control it every week. That's why my friend told me when CIS adjudicating cases, it comes with wave. If you miss a wave, usually you need to wait for a while. (I certainly hope it's wrong). But at least to my case, it is right. Of course, the Supervisor can change the priority of the case. But that comes in with the expedition which it has a lot of criteria.

I got this idea after reading this:
http://blog.wenxuecity.com/blogview.php?date=200708&postID=19650