i was watering once a day, and i dont think it was enough. now i water twice a day. maxx is right, its a good amount. a res under the unit fills a tray where the RW dips and wicks up water.
the reason you dont want it watering all day is because if the RW gets too wet, it will start dripping.
also watering at night makes no sense.
i oxygenate my res. i may not need too, but i also don't need to have ice cream for desert all the time. but i like too! no harm will come of it, and i have one sitting around anyways from my old DWC setup.
plus keeping the wool wet then spinning it in the air sure is a good way to make the room humid as hell. . . not that mine isn't already. also as it eveporates into the air, you will lose more res water, have bigger ph fluctuations, more ec concentration, etc. better to let it sit when you dont need to feed.