I have heard as well that even if you have that box checked, that Steam will still try to update when you try to play the game if it is in online mode, and thus to be sure it doesn't, only play the game with Steam in Offline mode.According to STEAM that option is only to keep the game from updating while you play --- It will still auto update the next time you launch Steam (Kind of a useless setting that they put there to let you think you had some control over what they do on your system !!) The ONLY way to stop Steam from updating games (or itself), is to block it at the firewall. When you choose to set the game to not update make sure to exit steam after, then start it again and check the setting.Games will re-enable update flags on a whim, Steam will even update games while in offline mode. Sometimes it doesn't save properly, but when it does (And I've done this with Skyrim) it will not update the game unless you change it back to auto update.High Priority: Always auto-update this game before others: This option will automatically give your game priority as compared to others when updating.
This is particularly useful because you can always set a time when you aren’t using your computer such as the time you sleep.
Another remedy is to disable Steam from starting up automatically when you turn on your computer.
As you may have noticed, Steam tends to start up whenever you turn on your computer.
This method is very effective and easy as you can toggle this through your Steam client without any hassle.
However, if you have a lot of Steam games installed, this can prove to be a tedious task.