In order to prevent automatic updates, you just need to disable them. Do it by following this post.
Besides that, you can check for updates when you don't work on an urgent issue on the machine, because the update process may take a long time (sometimes it takes hours!!!). Please notice that most of the updates are security updates and should not be prevented for good, and better apply as soon as possible!
Thanks Yoram. I wonder if that (3 Hrs update) happens only to me (open a lot of windows+ use office with macros etc) or also to more basic users