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.
On my first day I literally walk across the city, to the extent it can be done…The next day I do another cross town walk, but in a different direction, filling in the blanks from the prior day’s walk.
Then, over the next week(s), I walk between 10 to 20 miles per day, picking and choosing from what I have seen before, highlighting what I like, what I want to know more about, refining the path, till by the end of my trip, I have a daily route that is roughly the same.
While that is certainly not the most efficient way to see a city, it is the most pleasant, insightful, and human. I don’t think you can know a place unless you walk it, because it isn’t about distance, but about content.