As matty suggests, framer, it depends on what assumptions the Captain makes. If the Captain makes completely unreasonable assumptions about how ‘swimmingly’ the ATC system is going to work, and interprets all of the forecasts wearing a ‘pollyanhah’ hat rather than conservatively, I’m not happy theoretically.
But the new rules are going to ‘fix’ this problem. If the ATC system and forecasts don’t ‘work out’, the captain just declares a MAYDAY at 30 minutes calculated left on board, and we get priority. If I’m in a hurry to get into Sydney as a passenger I’d prefer the captain to plan on the ‘best case’, get stuffed around by ATC and inaccurate forecasts then get priority on declaration of MAYDAY due 30 minutes remaining.
All rules have unintended consequences...