The hassle of keeping your team tight

My partner and I go through the same issues every few months. We have a lean startup & we're in the early stages of development. Our entire team works remotely & I try to keep the dialog as an engaging as possible, while promoting my employees to speak their mind and innovate. The struggle we're having is keeping talent for more than a few months. I cant tell if the fire just stops burning for them or their is something we're not doing correctly. Some insights and advice would be great as I'm loosing patience in this grueling process.