Feel like I got here too late but, here it goes: I usually really worry about money and plan every big expense, but I traveled internationally for the first time last December and for the second time a few weeks ago and both were pretty rash decisions that I’m really glad I took. The first time, we just bought cheap flights to Santiago, but we charged them to a no-interest credit card and had savings to do it. The second, we had the opportunity to have a some-expenses-paid trip to Cuba and I really didn’t have money but my boyfriend did and offered to pay for me. I still spent some money (visas, health insurance, etc.) but it didn’t wreck my budget. Both times I was lucky to have some vacation days leftover at work.
For the next few years, we have decided to do what someone else already suggested: save for a trip and decide where and the exact dates once a really cool cheap ticket appears.
So if you really want to go to Australia you could start a fund and then stalk tickets. It’s not a once-in-a-lifetime thing. It’s a once-in-a-while thing. You just have to be ready next time it comes.