Mine doesn't grow mold but I live where it is extremely dry. I feed about 2 cups in the morning for 4 growing girls. I figure they finish that up anywhere between 2 and 6 hours. They eat every single speck of it. It just depends on how full their crops were when they went to bed.
I give about 1/4 of their morning ration in the evening when I let them out to free range. I live in the desert and our pickins are less than slim, especially in the winter. They have some dry grass, a few leaves and maybe some green weeds that are poking through the rocks. I feed the afternoon ration more out of habit than their being hungry. I don't like them going to bed with an empty crop. They spend about an hour free ranging now, sometimes a little more on the weekends and they will pick at the given food but forage for most of the time until it gets very close to dark then they gobble up what is left in the snack trays. The afternoon snack amount is dependent on whether I gave scraps that morning and how full I see the crops when I let them out.
If I make an apple pie or something they will get all the peels and the cores in the morning to keep them busy all day and when I get home from work, I can see they are not hungry at all. Afternoon ration is about 1/4 cup. Other days I have no kitchen scrap and they are itching to get let out of the run, race to the snack area then maybe they get a total of 3/4 c. I give scratch ONLY about once a week. I have noticed when I do (and believe me, they LOVE it, like crack cocaine!!!) they are VERY thirsty afterward. They just drink and drink and drink. That never happens on their regular routine. Given my dry climate and the super high temps in the summer, I plan to not give scratch at all come about May or once the temps are consistently in the 90's during the day.