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.
Design has very little to do with what tools or methodologies you use, or what your job title is, or what you have a degree in, or even anything like “creativity”; design is about your relationship to constraints. Rather: to what extent are you defining constraints rather than just obeying them? Design is about taking a universe of possibilities and converging onto exactly one outcome. Being handed a set of constraints which you treat like immutable laws of physics (because many of them are) and solving within that envelope is what engineering is. To wit: what most designers are doing most of the time is actually a form of engineering, and engineers are always doing at least some design.
This is because genuine design—the power to define constraints—is a privileged political position within an organization, and not everybody can occupy it. In other words, the “seat at the table” comes first. Design is Steve Jobs infamously dropping an iPod prototype into his fish tank, pointing at the bubbles coming out and yelling at his staff to make it thinner. It doesn’t matter what your title is; Jobs is the designer in that scenario.