17hrs 15 min NON STOP flight,,, no thanks. My recent 14hr flight with Etihad from Abu Dhabi to Brisbane was bad enough. The cramp and hard seating arrangement was torture, never again.
For my 16 1/2 flight to Australia, I just researched the seating (seatguru) and paid a little extra ($50) for the bulkhead seat. No one in front of me and I took a window and could just get up and walk around. It was very comfortable. I also had a stop en route...usually Vancouver. A night in a hotel is so relaxing between two long flying days.