Virgin Australia international check-in: 30-minute window?

Virgin Australia International Checkin, Why do they only provide a 30-minute window for check-in at some international airports (I'm talking about ones with only one flight at that time). I travel through Christchurch quite a bit and Air New Zealand open their international Checkin 3 hours before all flights (even the 6am ones) and then they close it 30 minutes before the flight departs. Meanwhile, Virgin Australia open it 2 hours before departure and then close it 90 minutes before departure. I can understand why at places like Sydney and Melbourne but at Christchurch where the maximum I've ever waited for security is 5 minutes I really can't understand why they have this blanket rule.

Virgin do not 'close' check in 90 minutes before depature.  From their website "You should be checked in for your international flight at least 90 minutes prior to your scheduled departure time."

Is that not that same thing?

"should" is different to "must".  Should means that you ought to if possible.  Must means that it is required, mandatory.

Okay... well, I challenge you to turn up 30minutes before your flight and have the "should/must" debate with VA check in staff.

As for the OP's point, the 30minute window VA encourages its customers to be checked in within, does seem pretty tight.

I've shown up 75 minutes before the flight and been rejected before so I would not try it.

Whereabouts?  That's a real concern because I understood QF was 40 mins before the flight leaves AKL (informally) and I aim at an hour for trans-Tasman.