Why confine this to "Under 35" ? I'm a bit older than that & I've been to Australia 4 times. I've a brother living in Melbourne for over 40yrs so the travel down under hasn't all begun in recent years.
Most of my friends, in their 40's & 50's have been too & even more people I know are going to visit sons & daughters on their travels. It's a great excuse !
It's a great country, with a lovely lifestyle & such vast differences in the different states.