Upvote:1
The visa that you get is not multiple entry, it is only good for one entry (and exit).
Regarding renewing/extending the visa - you can get a one-time extension, but this is if you are in Dubai and you want to stay in Dubai for longer than 30 days - you cannot extend it once you have exited Dubai - as the visa is only for single entry.
So it doesn't have validity once you have exited the country.
In other words, you'll have to get another visa when you want to come back in.
The visas are free for Australian citizens and there is no time limit between when you can get the visas.