I think the argument may be that it is cheaper to stop after, say, six and a half hours and refuel than burn the approximate '4% per ton' tanking penalty incurred if you plan a thirteen hour non-stop flight. I still think the extra wear and tear and cost of possible disruption, additional ground staff and flight crews, landing fees etc. etc. would outweigh the costs of non-stop fuel. Just my 2cents.
See what SIA do, they will have examined this scenario minutely!
