Everyone who is familiar with these batteries will hesitate to give you a firm answer.
For instance, I gave an acquaintance a pair of 14500 protected batteries and a charger, both brand new still in the package. He called me a week later telling me that while he was using them, a battery got really hot and the protection circuit board got so hot that it melted through the heat-shrink wrapping. He swore to me that he didn't short the battery, drop/pierce it, or expose it to high temps.
Any number of things can go wrong, even with a protected battery. I have heard of low/medium quality
CHARGERS bursting into flames. Imagine placing your batteries into the charger, the charger overheats and ignites, the flames reach the batteries, the batteries pop and vent, an ember lands on something else...
That being said... I have been known to charge overnight occasionally.
My advice is if you choose to charge them unattended, do so in a safe manner.
What I do is place the charger on a fire-resistant surface, (the tiled floor of the bathroom), and cover it with an old flower pot I have lying around. I run the wire though the hole that is in the bottom of it. Clean up the immediate area surrounding it, (I don't leave the garbage can filled with tissues next to it), close the door (and make sure you have working fire detectors). If these things don't stop a fire from occurring, at the very least they will give you a bit more time to avoid having to visit the burn unit. Having a fire extinguisher close by wouldn't be a bad idea either.
I'm not saying that you need to be terrified of charging them, I just feel that promoting awareness, vigilance,and safety is the best policy. No one wants to hear about the very first e-cig related fatality ever being caused by a lithium fire.
Take care and be safe,
-Dee