We have built an MVP and have some seed funding. Our vision for the company is well-aligned with our investors’, but I think the time will come soon when we need to stop iterating based on our own ideas and begin mining for and applying our users’ feedback. I’m assuming some of this will be useful, and some of it will not be very useful. I really don’t want to fix something that isn’t broken. That seems like a bad use of our time and funding.
How do you know when it’s the right time to institute user feedback? Does something have to be “wrong” or struggling? Or is there just a time when every startup should start listening more to its users, even if that means drifting away from its original vision?
From day one. However, do not bother if you are not interested in the feedback. Users can tell if you are interested in the way you ask and when and if you follow up personally, not just the cliche "Thanks! Your feedback is important to us." email. That is BS. If I am willing to help you with your product, you owe me the respect of a personal reply; preferably from the (real) CEO, not Stacy/Matt in customer service.
I'm mildly surprised you didn't speak to people before you started building your product. Creating a product should be a collaboration between you and the people who are going to use it - after all, they are the ones who will hopefully give you money.
Of course some feedback will be useful, and some will not. Your job is to synthesise all of that learning and use it to guide the product forward.
I laugh at the arrogance of some startups who adopt the 'we know best, what would the customer know' approach. There is no question from time to time you need to have the courage of your convictions, stand your ground, and say "I believe this is what the customer needs", because you are endeavouring to anticipate the future, and sometimes customers may not, at first, see the future the same way as you.
Absolutely from the moment you have your idea and certainly all the way through building a product. Ask for advice. Suggest ideas that you've had and ask if they would be useful to your prospects and then iterate, release, get feedback, repeat.
What you describe as 'YOUR' vision will fall flat on its face if your customer base doesnt share that vision.