god I hate rockwool. That shit just hold too much moisture. In hydroton I flood for 8 minutes every 3 1/2 hours. No floods at night. In rockwool I would flood however long it takes to flood to the correct level and do that every 4-5 hours. No floods at night.
BTW There are many theories on the whole 24/7 light regime but ask yourself this...on what planet have plants evolved to grow in constant light? You will see better root growth with 18/6. Your HID bulbs will also last longer. Doesn't matter in the least to me, just putting it out there.