I have wondered this as well (international to domestic, rather than international to international as OP situation) and have avoided some flights back into NZ where I would have had 5 hours or so to fill in, during the wee hours of the morning in Auckland as was not sure if I could collect my bags and stay airside at international (assuming domestic terminal would be closed) .

Just out of interest what is open (if anything) airside at that time of night/morning?