I did this a few years ago with my crock pot. I called it "perpetual porridge" and kept it running for about three weeks.

The first few weeks were sensible: I made a soup and added root vegetables and water. Sometimes some sausages and beans.

I do remember the mistake: adding a super old (not moldy) half loaf of sourdough for it to chew through.

From then on it was spoon after spoon of funky sour. Haven't tried it again since.

Seems like a great strategy for clear broths though!