Battery drain overnight

I doubt it as well, because like I always say, I don't have this issue, and I have never had it. Everyone has different settings applied to their phones. Everyone also uses their phones different as well.

My phone is still going more than 16 hours after it's been off the charger.

Nick_ahir wrote:

... without any use.

I seriously doubt this. You're probably doing a whole lot in background.

About the battery usage on your iPhone, iPad, and iPod touch - Apple Support