I really found this video on the mark with our experiences with long haul travel with toddlers.
Suddenly that trip to the over water bungalow in the South Pacific seems less appealing.
I noticed the advice on the video advises parents to have toddlers go to the bathroom before traveling on planes to avoid the attraction of wanting to go back. In contract I prefer to move around regularly on planes and engage my little girl in as many experiences as possible. Personally I find it is easier to meet her needs in this way rather than try to put a lid on them. We managed a 36 hour journey from the Australian rain forest to the Canadian winter by doing this with one happy child all the way.