I suspect you would go through some stages, the first being fermentation. Once the food is exhausted you don't have bread dough anymore, you have goo.
For instance, my starter (100% hydration) is a fairly slack dough. Once the food is exhausted it is just a goo, very liquid like. If you let that sit it will form a hooch on top, the alcohols rising up. Then it gets moldy.
I think, in the end you have to worry about mold more than spoilage, but by then you don't have a useable dough.
"First you start with a pound of bologna..."
-My Grandmother on how to make ham salad.