Either will work. I have done as little as two days, and went as long as two weeks. The main benefit to a shorter time frame is that the cricket eggs will hatch closer together in time and thus be a more uniform size in the batch. The other thing is that the crickets will dig into the soil and eat some of the eggs, so you potentially lose some, but that is really no big deal considering how many eggs they lay to start with. The last time I bred crickets, I just used clear containers for the egg laying medium and when I looked at the sides and it was packed full of eggs, I would remove it. Didn't pay attention to how long I left them in with the mature crickets.