Hi - I see a lot of great responses.

I've started a lot of businesses, currently CEO of a biotech/AI company. My quick answer that is you should do market and customer validation all the time even when your start-up is only a glimmer in your eye. Market feedback is like gold! It can help guide you and help you avoid going down rat holes. The discipline is to listen, learn, act or decide not to act.

As you start committing more time, money, and resources into your venture, market and customer validation becomes all the more important. As your venture develops so will your offering so you can go from a concept to something more tangible for customer to react to.

Set-up a call and we can get more specific if I know a bit more about what you are doing.