Hey Ogz,
The main reason why people get other people to run the car once a week while their gone is to keep the battery charged up. While you are not using your car, your alarm system, clocks etc are still running. Most people will just get someone to turn on their car, leave it in idle for about 5-10 minutes once a week.
That being said, I've left my car untouched for two weeks, coming back from Holiday and the car started without any issues. But that also depends on the condition of your battery.
The other thing I've heard people do is just unplug their battery before leaving, this will stop the car from draining it while you're gone.