What are you feeding? Corals? I don't turn my power heads off ever. I used to have an oceans motions 4 way that was fed by a reeflo hammerhead on a 195 reef. This alternates current very effectively, without the use of power heads. I didn't see any coral growth differences between that tank and any other I've kept, so I don't see the use.
Btw, mesh guards on your power heads or not, if an anemone hits one, it's definitely going to get sucked in and all tangled in it.