309 Visa Approval - conditions to keep in good standing

Hey all,

My wife is American and we were thinking about applying for her Australian Partner visa whilst we are still living in America. We have plans to move back to Australia but they are tentative and the timeline is still real approximate, a lot of people have suggested apply offshore, I was wondering about the conditions once you have been granted. I know there is a entry date that you must enter by which activates that visa, is there a minimum amount of time you have to stay in Australia to keep that visa in good standing, i.e. could she be approved for the visa, we goto Australia to get her stamp, would she then have flexiblity to travel in and out of Australia as she pleases if we're still in the process of tying up loose ends over in the states?

Thank you so much for reading this and any advice you might have,

Greg