I've had my Droid 4 since a few days after they came out, and today, for the first time, I got a low battery warning. Alas, it is charging as we speak.
The cause: for the first time I used the device for vehicle navigation (using the stock navigation app that came with the D4 -- which I really like) and I failed to plug in the battery charger in the car. That app uses the juice, 'cause it spends a lot of time doing GPS calculations and naturally, it runs hot. Will not make that mistake again.