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.
In the television show Masterchef there was an episode where the judges did a test on what they call “basic skills”. One of the judges often says that in order to be a “true chef”, you must know how to quickly and finely cut onions.
...This was really bothering me and I am stubborn so I wanted to win this fake argument really badly so I looked up why the way one cuts onions is important: as it turns out, the shape and even the surface area affect the end flavour. I thought the whole “chop chop chop” was about performance in the kitchen. Cut quickly to serve quickly! I was wrong.