It’s critical to get your feedback from a variety of sources. The longer you solicit your reviews from the same panel, the more danger you have of simply adapting to that one specific audience.
A small sample size is a bad idea for any data collection. There’s no guarantee that the feedback you’re getting from a tiny group is valuable! You may have stumbled upon a niche faction that loves (or despises) everything you do, which means you’ll settle into a rut. You can’t improve without broadening your horizons.
Get out of the bubble, and expose your work to unusual feedback. Go as broad as you can, even if you’re searching for a target demo that’s much smaller. You can find it within the feedback you receive, but that initial feedback will be invaluable.
The Opportunity Machine 