We've just spent 2 fantastic weeks in Florida doing all the theme parks (and the 9 hour flights in both directions) and we are both so proud of our (soon to be 4 yr old) daughter..... She coped so well and told us when she had enough. We kept to a reasonable routine and it all worked so well. we'd been extremely nervous about it but it went like a dream. Yes, we had some potential flashpoints but we worked round them and it meant that we all got to have a fabulous holiday. we even managed to eat in a restaurant one night without any major incidents.
And to cap it all, she wrote her name on her own for the first time without any help whatsoever. It really made Father's Day!