Back in our grandparent's day, growing up used to mean marriage, kids, and a mortgage. But a generation later and it's not so cut-and-dry. We're happily living de facto, having kids later (if at all) and let's not talk about the state of the housing market.
But in spite of this break from tradition, there are certain things you just don't do once you hit 30.
And if you need a refresher, we've prepared this list:
1. Live like a student
Any share house situation involving turntables, grime encrusted showers, and coffee table bongs is a cry for help.
Who are you talking to on Snapchat? Unless you work in advertising and are trying to sell Kardashian brand make-up to 20-something Cosmopolitan readers there's absolutely no justification for this.
3. Energy drinks for breakfast
There's a fine line between adventure and a death wish. If you really want to gamble on the future of your kidneys at least pretend you're an adult and hide the contents in a mug.
4. Ask friends to help you move
The only thing worse than moving house is helping someone else move house. Hire some professionals to lug that bookcase up two flights of stairs in the middle of summer.
5. "Couch surfing"
Are you a German backpacker on a gap year from university? No? Then get a hotel room.
6. Unframed movie posters
Because nothing says success like a faded Reservoir Dogs poster on the wall.
7. Bring home hard rubbish
Never okay, but if you're still doing it in your 30s you've officially graduated to 'wretched poverty'.
8. Iron your own business shirts
It's boring and time consuming. The local laundromat will wash and iron your shirts for about $3 a pop. It will change your entire life.
9. Clean your own shower
As above. Hire a professional and spend the time doing something constructive with your life.
10. Buy fringe political magazines
Sorry to burst your bubble Che Guevara, but that ship has sailed. If you want to change the world consider joining a political party, writing a book, or doing some volunteer work.
11. Adventurous haircuts
You're not a Portuguese footballer player.
12. Modified cars
Drive a car that has been lowered, modified, plastered with stickers, or otherwise altered to resemble something out of Tokyo Drift? That Nissan Skyline you loved in your youth doesn't send the message you think it does.
13. Obsessive gaming
We're not saying you can't play video games, but if you have 40+ hours in any given week to level up your elf it's time to reassess your priorities.
14. Eat like you did in your 20s
Your metabolism slows down in your 30s and that chicken schnitzel roll from the Vietnamese bakery is not helping your 'abs of steel'. Try and work some salads, soups, and sushi into that lunchtime rotation.
15. Dress like a d--k
We know you loved electro house and had TV Rock's Flaunt It as your mobile ringtone, but that was a decade ago. It's time to retire the skinny jeans, plunging v neck t-shirt, and flip-flops ensemble.
16. Get news entirely from Facebook
The problem with social media is that you end up in an echo chamber of shared beliefs and bias. If you want to know how the world actually works you should visit some proper news sites – especially ones that have a different political slant to your own.
17. Drink terrible booze
You can force down a $10 bottle of plonk and wake up feeling like hell. Alternatively, you can spend a little extra, enjoy your drink, and receive approving nods from friends while you refill their glasses.
18. Have boring friends
The people you surround yourself with reflect back on you. Holding on to bored, broken, or otherwise toxic friendships doesn't say much about your self-esteem or sense of worth.
19. Post drunk photos
Most recruiters will do a quick social media check when considering potential applicants. Instagram evidence of your hard boozing lifestyle is unlikely to impress them.
20. Avoid the dentist
Yes, we know it's horrible. But avoiding the dentist is only going to make it that much worse when all your teeth look like Swiss cheese in a few years time.
21. Wear ill-fitting suits
If you want to get ahead in the world you need to dress the part. A cheap, ill-fitting suit tells the world you don't care about details, good taste, or first impressions.
22. Any kind of 'tabletop' gaming
In the immortal words of Belinda Carlisle, "Live your life, be free." But as far as the outside world is concerned you spend your weekends playing Dungeons and Dragons while knee deep in Doritos and Mountain Dew.
23. Talk about high school
It's been at least a decade, if you haven't done anything worthwhile since then it's time to find a little direction.
24. Holidays in Bali
There's a whole world out there for you to explore. Why are you on Kuta beach in a Bintang singlet with a bunch of other Aussies?
25. Run out of alcohol
A happy home is a well-stocked home. You'll need one bottle of the following – Vodka, scotch, tequila, gin, white wine, red wine, rosé, Champagne (from France). Don't forget the ice and the single serve mixers.
26. Get into online arguments
Nothing you say is going to change anyone's opinion. Step away from the computer, take a deep breath and walk around the block, you'll feel much better.
27. Appear on reality TV
You know it's probably going to end in tears and public humiliation, right?
28. Questionable jewellery
A nice watch and a wedding ring are fine. You can leave the shark tooth necklace, Red Kabbalah string, and gold bangle in whatever spiritual purgatory you found them.
We'll allow a couple, but if your social media feed is 80 per cent duck faces at the camera, perhaps dial back the narcissism.
30. Listen to bad advice
Take life advice from random lists you find online? If you're over 30, you might take them with a grain of salt.
What can't you get away with after the age of 30? Let us know in the Comments section.