The ROSO (Return Of Service Obligation) is 10 years from graduation at 2FTS. Add on 2 years of training (at least) before graduation and 11.5 is probably an understatement of your commitment.
If the pilot decides they dont want to fly they get shafted to a ground job. Not always in a preffered location. Choosing not to fly is definately frowned upon, unless there is a good reason, family etc.
If your not sure about the long term flying in the RAAF dont waste your time (and the RAAFs) applying, they will pick you out a mile away.