How long is the trip

You should allocate at least 3 hours to see everything

I agree. Between 2 and 3 hours does the visit justice. Well worth the time. Truly historic.

I agree. I did it in 2 but 3 hours is a safe bet

Kind of up to you. Minimally, two hours, but 3-4 for full experience.

I just listened to the main portions of the guided tour and was done in 2 hours.

I completed the 6th floor in four hours time. There are more exhibits on the 7th floor. Allow for most of the afternoon.