The idea is that you can control when patches are installed and systems are restarted. Sometimes it is very important to know exactly when a system will be patched/restarted...
However, I would recommend what we do for most of our workstations. We have the plug-in policy set to install every hour. That way if any updates are scheduled they will install within the next hour. You can also use a window instead of a scheduled time so you have several options for scheduling.
Attached is an example of our Desktop Software Update Plug-in Policy... When we need to reboot the systems, we simply hop in there and change the date for the restart section, as there is no repeat it will only restart the systems within that window on that date.