We typically recommend the speakers to be powered down if they're not going to be used for ~12 hours or more. You also want to power them down if you're experiencing an electrical storm or other conditions that might prompt a power surge.
You can definitely leave them "always on" and toggle power from a smart plug or power strip etc. There is not risk in doing so! Please note that you may hear a "pop" when powering on or off, due to the normal shutoff sequence being bypassed. There's no risk to the loudspeaker if this happens, and we have several protective measures in the design to compensate.