Besides some electives, most of the class attendance in the summer months aren't compulsory. There is a 1 week break between the end of Tri 2 and start of Tri 3, a 2 week Christmas/NY break in the middle of Tri 3, and a 2 week break between the end of Tri 3 and start of Tri 1. Depending on the elective you choose, it is entirely possible to go home during trimester 3 if you're an interstate or international student once you have completed the compulsory components of your elective, you will just be watching the lectures for the remaining courses online (and missing out on some tutorials).