I'm here on a 3 month visitor visa. Do I have to leave the country before the three months is up?

The current policy is that a person may remain here as a visitor for up to 12 months provided they are genuine visitors and have a return ticket and enough funds to keep themselves. Visitor visas are not intended to help you to meet the 12 months relationship criteria.

However, if you want to stay past the 3 months allowed on most visitor visas you can apply here in Australia for a further visitor visa. This will override the multiple entry visa you arrived on and will have a fixed expiry date. Although you will be able to travel overseas you should understand the fixed expiry date on this visa. Visitor visas granted onshore are usually for 6 months. It now seems Department policy is to put the 8503 condition on further visas granted in this way and you will not then be able to apply for further stay after that visa expires.