How long do you let moonshine ferment?

It all depends really on things like amount of yeast, MASH, temperature, etc. But usually it'll take abut 4-5 days. To be sure, wait to distill until the mash has stopped bubbling and it has a really sour taste. Fermentation speeds up at higher temperatures, but make sure you don't let the temp. get above 120F or the yeast will start to die, which means theres nothing to produce alcohol.