I would not want to do it that way. I think that eventually the ferment would be over mature, and you'd actually end up loosing the nutritional benefits. What you're suggesting, is that when the feed is getting low in the barrel, you add more feed and water? I think it would depend on how well you stirred it up from the bottom. If it never got used up from the bottom, I'd not be comfortable with that. But, I'm interested to hear from the folks who do use a large bulk of Ff on a regular basis. How many birds are you feeding?