Roughly 1.5 hours, including time asking questions after the basic tour.
The house is rather small on the inside and only a few rooms you'll tour most of the rooms you will not even enter Because they have them blocked off so you're only looking in to the room. We went during October last year and there was no waiting. So it was no more than 30 minutes inside the house. About 90 minutes walking the grounds and taking the trail tour. We weren't in a hurry but if you are you can do it faster.
I would bank on about an hour from a possible wait at the door to hanging out in the backyard of the house at the end. The time usually depends on the guides in each room and how many questions are posed.
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