Yes and yes. You can tell when they have too much when their urate has a yellow tinge to it. I don't know how long this has to go on for it to become bad, but once you see it, back off a bit. A good way to remember how much, for younger beardies, one feeding a day, 5 days a week dust all the feeders. If they get to the 35-40 mark, you can probably stop there for that day. That's more of a guess than anything. But don't worry too much about overdoing it until you see the yellow urate. And also give lots of baths.