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 all cases, a commonplace is a method of compiling knowledge for later use. In digital or analog form, this continued growth of stored ideas and projects is a key driver of intellectual development. Any time you decide to work on a project, you should attempt to collect and categorise all information that is relevant and useful.
Methodically noting and filing resources is a sign of a mature and deliberate craftsman—it is an investment into future learning and projects. Before long, you will begin to reach the point where this collection generates projects and ideas with minimal effort; previously isolated ideas are consolidated and curiousity spurred on.
Effective writing stems from intelligently connecting the dots between the concepts you understand and can articulate. It stands to reason, then, that in order to generate more creativity you must not only add to a knowledge base, but deepen and expand the number of connections within the totality of the network. By establishing and explicitly mapping your knowledge, you allow yourself the freedom to remix information. You will often find that solutions come from previously unsuspected fields or topics—proving to be analogous in some shape or form.
Richard Feynman was fond of giving the following advice on how to be a genius: You have to keep a dozen of your favorite problems constantly present in your mind, although by and large they will lay in a dormant state. Every time you hear or read a new trick or a new result, test it against each of your twelve problems to see whether it helps. Every once in a while there will be a hit, and people will say: ‘How did he do it? He must be a genius!’