I did Sydney to London and it was around 20 hours in flight. I don't think anyone should wish for that trip without a stop in economy class.
I'd gladly pay extra for a direct flight, because...
- 4 hours quicker
- An aircraft issue at Dubai can add a day to your journey (as happened to a friend who visited at Christmas)
- Changing at Dubai always seems to involve twenty minutes of walking, ten minutes on a train to go between terminals and then ages on a bus to get from the gate to the actual aircraft. Total PITA.