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.
As soon as Te Shan crossed the threshold he said, "Long have I heard of Lung T'an (Dragon Pond), but now that I've arrived here, there's no pond to see and no dragon appears." Master Lung T'an came out from behind a screen and said, "You have really arrived at Lung T'an." Te Shan bowed and withdrew.
During the night, Te Shan entered Lung T'an's room and stood in attendance till late at night. Lung T'an said, "Why don't you go?" Te Shan bade farewell, lifted up the curtain, and went out; he saw that it was dark outside, so he turned around and said, "It's dark outside." Lung T'an lit a paper lantern and handed it to Te Shan; as soon as Te Shan took it, Lung T'an blew it out. Te Shan was vastly and greatly enlightened.