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.
What keeps me busy in my classes is trying to help my students learn how to think. They say, "Rob holds his hands like this...," and they don't know that the reason I hold my hands like this is not to make myself look that way. The end result is not to hold the gun that way; holding the gun that way is the end result of doing something else.
…The more general issue is that a person who doesn't understand the thing they're trying to copy will end up copying unimportant superficial aspects of what somebody else is doing and miss the fundamentals that drive the superficial aspects. This even happens when there are very detailed instructions. Although watching what other people do can accelerate learning, especially for beginners who have no idea what to do, there isn't a shortcut to understanding something deeply enough to facilitate doing it well that can be summed up in simple rules, like "omit needless words".