AFAIK, the only way to truly turn them off is to remove the battery or cut the positive lead and splice in a switch. Only drawback is the switch has to be on for it to be able to charge, so that's a bit awkward. The "soft off" when you hold the power button is just deep sleep.
Mine frequently wake up from deep sleep but not after 5 minutes. More like 3-4 days. Which makes keeping a few always charged difficult.
Edit: I just checked the Power settings in the app (they've changed it a bit since I set mine up). The longest it can deep sleep is 72 hours it seems. Maybe yours is set to 5 minutes?