We have friends that recently holidayed in Australia, with an 18 month old and a 4 year old. They took direct flights from Melbourne to London, as they felt even though on the plane for so long, at least there could be more of a routine whilst on it, rather than adjusting to new time zones on the way home.

We haven't done this ourselves, but it seemed pretty logical. It usually seems to be that actually being on the plane is the easy bit, and that it is all the kerfuffle getting on and off that can cause trouble.