If my DS is happy & having a good time (which he usually is), we stay.
If he is tired and cranky, we leave. Simple as that.
My DS usually LOVES the late nights though. The later the better for my kid.
If we do a late night in the parks, we sleep in the next day. We also, always go back to the hotel for a nap mid day. At home my DS naps about 2 hours a day. At Disney, he sometimes naps 4 hours or more. And that is fine. After his nap we head back to the parks & can do the EMHs, because he had such a long nap. And he is thrilled to keep going.
I dont know why people keep going when their kids are obviously tired & not enjoying themselves.
I mean, if your kid is up for it, go as long as they will. But if they are crying, cranky, or worse, it is time to call it a night. Simple as that.
We did the EMHs when we were there last week. MK EMHs started at 9:00pm. By 10:30pm (9:30pm our time), we had ridden everything we wanted to & headed back to the dock for the boat back. DS was having a great time. But we had ridden everything, and we could tell, he was just starting to get tired (some of those cranky signs were starting to show). So rather then push through for another hour & a half, with an increasingly cranky & tired toddler, we called it a night. Went back to the hotel, DS fell right to sleep & was well rested for our next day out.
Even if it is a "once in a lifetime trip", there is no reason to push a kid to where they are so tired, they are just in complete meltdown mode. What fun is that for kid or parent?
If you miss a ride, you miss a ride. But your kid is happy & the memories of a happy kid for a lifetime, are better then a stressed out parent & an incredibly tired cranky kid at that moment.
And when you look back, do you want the happy "Remember when little Timmy had so much fun in the MK?" or the "Remember that night Timmy was so cranky he cried so hard he threw up from exhaustion"?
My DS is a natural night owl, like his parents. So we can always stay late in the parks. He just loves it.
But if he is tired, we go back to the hotel.
Everyone needs to be happy for the trip to be a good one.