Once you've been in Aus for 2 years you can apply for PR (actually, I think you can do it before 2 years, but the criteria are a bit stricter). Once you have PR, you can move jobs without worrying about visas.
You can also start the process before the 2 years ie getting the police checks, medicals, filling out the forms etc so that you're ready to submit pretty much on the day - this process can take a few months to do, so worth starting early if you're keen to move jobs.