10-20% in a day!!? seems if that's true, you may have some other issue. I have left mine for upwards of a week & seen less than a 15% drop in battery.
To solve your problem with the button firing mode and it accidentally firing somehow, you can rapidly click the fire button 5 times to engage a fully locked, un-puffable state, right?
I'm not sure if you're a seasoned DNA owner or not, but none of them (that I own or am aware of) actually fully and completely "power down" in the traditional sense. They generally will fall into the the sleep state James mentioned, and in this state, they consume comically small amounts of power. Of course, people should remove their batteries if not planning to use their DNA mod for a length of time on applicable mods , but The One, easily has the most run time - and consequently, the most standby time out of any pod system in my collection.
So yeah, just manually lock it by pressing the fire button 5x, like all other products made by Evolv. Drain will be negligible & accidental activations become nigh impossible. Also, you may want to submit a ticket if you're truly seeing up to a 20% decrease in standby battery drain over a 24hr period. That is not even close to what it should be under reasonable environmental conditions. I don't lose 20% using it for the day, I believe last I misplaced it for around 5 or so days, it was around 82% when I found it almost a week later.
Cheers! hope you find the solution you're looking for!