Australian Citizenship and Resident Return
Permanent residency is a status that entitles a person to remain in Australia indefinitely.
The grant of a visa can give you permanent residency status. The visa
is simply a travel authority that allows you to fly in and out of Australia for up to 5 years while maintaining your status. If you are in Australia when your visa expires, you are still a permanent resident. If you never left Australia, you would never need another visa.
However, if you are overseas when your visa expires, or you leave Australia after your visa has expired, then your permanent residency status will cease.
If you want to continue to travel overseas after your visa expires, then you need to apply for a Resident Return Visa or obtain Australian Citizenship and an Australian passport.