If you want Windows to shutdown without waiting, open the Run window with Win-R and type:
shutdown -s -f
-s causes shutdown (You can also use
-r to reboot).
-f tells the computer to ignore all programs screaming protests that they need more time.
Windows 8 generally waits to shutdown because a file has not been saved or a program is waiting to finish executing, you will want to find out why and deal with the issue at its source. Waiting up all night for a response is often better than closing an important unsaved file that the user might need, hence why Microsoft set the default as it is, with the option to simply press the force button to shutdown your computer anyway.
If you want to do this anyway, I recommend putting the above in a batch file on your user's desktops, otherwise they might shutdown for the day in the normal way and lose an important file unthinkingly.