When your BVB is granted, we will tell you when the specified travel period will end.
If you hold a BVB where the specified travel period has ended but you need to travel outside Australia again, you will have to apply for another BVB.
When the specified travel period of your BVB ends, if you are still outside Australia the BVB will end and you will not be able to use it to return to Australia. If you do not also hold a substantive visa that lets you return, you would have to apply for another visa before you could return to Australia. There is no guarantee that you would be granted a visa.