I would say 4 to 5 hours to really take it all in. There's really a lot to see and read about, not to mention the the short videos and mini movies. So perhaps, 5 to 6 hours should cover it.
It depends if your are a reader. I went with my teens and they got tired of waiting for me. There is also an app where you can get more information per display. I could have been there all day.
2 1/2-3 hours
Depends on your preferences. We spent 3 hours with 2 ten year olds and 2 adults. I would suggest an hour a floor and additional time for a special exhibit.
About 2 hours
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