Once you see that an answer is not serving its question properly anymore, it should be tossed away. It's just their natural life cycle.
They usually kick and scream, raising one hell of a ruckus when we ask them to leave. Especially when they have been with us for a long time.
You see, too many actions have been based on those answers. Too much work and energy invested on them. They feel so important, so full of themselves. They will answer to no one. Not even to their initial question!
The hardest thing about customer interviews is knowing where to dig. An effective interview is more like a friendly interrogation. We don’t want to learn what customers think about the product, or what they like or dislike — we want to know what happened and how they chose... To get those answers we can’t just ask surface questions, we have to keep digging back behind the answers to find out what really happened.
Arturo Soria y Mata, who proposed a linear streetcar suburb for Madrid in 1882 and managed to build something like three miles’ worth of an intended thirty. Likewise, the project by Edgar Chambless for Roadtown, published in 1910, depicted an infinitely long, two-room-wide building atop three levels of underground rail lines for express, local, and freight traffic. In the late 1920s, N. A. Miliutin proposed a Soviet Union–spanning linear plan that—following Soria y Mata’s rhetoric—would have solved the old Marxian chestnut of city/country contradiction at a stroke. Le Corbusier’s Algiers scheme of 1933—a highway-topped fourteen-story building meant to stretch miles along the Mediterranean and house 180,000 people—was surely the most immediate precursor of Rudolph’s “City Corridor.”