Here's a simple way to make your own self-feeding fire to burn 12-15 hours.
If you're camping or in a survival situation where you don't want the fire to go out but you might not necessarily have the resources to stay up through the night to tend to it, here's a way to build a ramp style fire pit that self feeds logs evenly.
Set up 2 ramps across from each other and load them with even-sized logs. Insert spacer sticks between the bottom logs to ensure and even burn and proper ventilation. The ramps can be made of wood, or steel.
Pay close attention to how Bob Hansler lights the tinder fire in the video, as he stresses how the logs must burn evenly for the wood to continue to self
Here's the video that shows it in action:
This is a creative way to build a campfire, or a survival fire if needed.