There's no set time, the example I gave above was just that an example. As Htchien pointed out if you add a lot of transitions it will take longer. Even two machines with the same CPU can give vastly different results if they have different mobos or other different components. The amount of time is subjective to your particualr machine and configuration and what your doing with the video. the only way to find out is give it a try but don't be suprised if it does take 4 hours.
You can optimize your computer for video editing by disabling unneeded background tasks.. start here
www.blackviper.com
Additional speed boosts can be accomplished by overcloking your CPU, There's many tutorials available on the internet on how to do that.