I know a couple of hydro growers that run the nutrient 24/7. The roots will grow quite a bit. One grower uses 12 litre buckets and rocks for a medium, he needs to keep an eye on the drains because the roots will plug the drains.

The other grower uses PVC pipe with net pots and vermiculite for a grow medium. Once the roots are hanging down to the bottom of the PVC pipe he puts the feeder lines at the far end of the PVC pipe. The roots grow all the way down the PVC pipe and in to the reservoir.

Good Kannabis Growing!