It's a good idea to do this before a big event, like the day before an important presentation. If you want to make absolutely sure that Windows won't update at an inappropriate time, take matters into your own hands and run Windows Update manually.
But this will only work if you leave the computer on during the non-active hours. You can avoid the worst of this by adjusting Windows Update's active hours, which specifies a period when an automatic restart supposedly won't take place. Sitting through an unwanted update can involve an unwanted restart and will take up your time and internet bandwidth. If you use Microsoft Windows, you can likely relate to my colleague Sean Hollister who recently documented at length the number of times that the automatic Windows Update feature has caused him pain.