There are two possible reasons why each conversation feels like a new conversation.
1. You are at the very beginning of a problem selection and segmentation exercise.
You are casting a very wide net - talking to 30, 40, 50 people in many hypothetical segments. What you are doing is to "boil the ocean" and use the interviews to help you understand how people self-organize, and help you create the right behavioral segments for your new venture.
In that case, it is good that you are hearing new things - that means you are still learning where your segment boundaries lie. Keep doing it until clear patterns emerge.
2. You are well past segmentation and beachhead market selection and believe you are interviewing to build a tight persona.
You are interviewing a carefully curated list of people, and yet you hear very different things in areas where you expect shared needs and wants. In that case: What this means is that your targeting is either too broad, or you have created a hypothetical segment and persona that does not quite match how your potential customers see themselves.
Step back and ask yourself how else you can sub-segment your target market to tighten it up. See if you can have lots of short conversations with lots more people to help you sub-segment. You will probably end up having several tighter targets, each sharing more nuanced attributes with each other. Now you can recruit a few people per target and look for the sweet spot.
This article builds on content developed by the Martin Trust Center for MIT Entrepreneurship for MIT's Orbit Knowledgebase and is licensed under CC BY-NC-SA 4.0.