I actually haven't even enrolled in any of my subjects because I was still thinking about breadth. 
I'll be staying up tonight as long as it takes lol. What happens if I don't enrol in any subjects by tomorrow?
Technically you have until the 31st of March before the census date for enrolment, but you will have missed 3-4 weeks of class by that point, and if you're wanting a concession card you really have to sort it out by the end of February.
Administratively-speaking, I don't believe anything will happen in that you won't be thrown out of uni or w/e, but if you're not enroled then you can't register for classes, and if you take too long to pick them then they might fill up, and you'll either have to pick different ones, or end up in the awfullest tutorial slots (i.e. 8 in the morning and 6 in the evening

)
Have you narrowed down your subject choices at all? I'd seriously recommend just choosing a sample platter of interesting stuff and/or prerequisites and enroling in that - otherwise you'll be left hanging tomorrow (assuming any of us get in at all).
At least enrol in the ones you know you want to do; you can sort out your breadth later
