Glad to see it's happening to everyone, else there'd be something to worry about 🙂
Personally, my test device is currently at 13% at 5pm, usually it'd be around 60% so the power usage sure is off, but the point is that it does not matter. As has already been said, there's likely no power conservation going on right now, and I'd expect low level logging is active.
Leave the device plugged in all day (like I will be tomorrow!!)
As for "development device only" I fully agree, yet I happily install on my primary iPhone6 because that is my dev device. If it breaks or goes on fire, I have a perfectly good iphone 5S that I can live with. Hard to get to grips with an OS and do testing if you dont actually use the phone! So yeah, installing on primaries is fine in my opinion; but only if you dont really care about things like data loss and power loss !