Water 24/7 ?

Do you need to run water 24/7 during both cycles or either one or not when the room is dark? I've been running water only during the day cycles with good results. Thanks

I run a DWC/Top water feed and i have a constant flow of nutrients 24/7 and have had good results but i have found that i have to mix my feeds at a lower ppm due to this constant flow to prevent nute burn but this might change with different brands of nutes. Also dry spells are good for roots to get oxygen i think its just personal prefrence