A short-term review of this setup. So far, I don't think it will drain the battery. I park on street and I'm getting maybe 1-2 recording per day, if any. Although most of the time for no reason at all as I haven't seen anything touching the car. I've set sensitivity on high and tested bumping the car myself and it didn't record, I'll have to test more. So, I don't think there's a risk draining the battery but I'm not so confident it will record when needed. We'll see.
Beautiful setup though, only the small rear cam slightly visible, every else tucked away.