How long should you run the water through the kitchen disposer before you can be reasonably assured that all the stuff has been washed out of the plumbing?

Once I had drain flies. Not a big problem, and it was great killing them. But who needs that shit.
I have a suspicion that I am underestimating how long it takes to flush the plumbing that empties the disposer.
I bet it might be dependent on what gets chopped up in the chamber.
But I don’t know for sure.