I've had great results leaving them running 24 hours, can't really OVER water with the hydroton, they could just run 15min ON every hour too. either way will work.
That's a nice little thread. I like how you put the shut off valves on. I'm gonna have to do that. I just modded my controller so it will recirculate threw all the reservoirs.
You might want to drill some more holes in the first bucket for better drainage. There is a thread around here somewhere with waterfarm modifications and tips.
I run my drip ring all the time during early growth once the roots reach the bottom bucket then I cut the drip ring back. My plants can take it, because they have alot of light.