When an Open Inspection never Closes

I was driving home this morning and I noticed this Open Inspection, I laughed all the way home grabbed my camera and ran down the street hoping the sales rep would not pack up and go.

When I arrived I said "I have to take a photo of this, it's the funniest thing I have seen in ages."

He said "he had held an open inspection on a vacant lot of land, and that's funny".

So when does Open Inspection become closed when there are no walls and no roof?