The is no problem in leaving the phone charging overnight. The control module will turn the charging off once it will reach full capacity, and periodically will turn in on once battery measurably discharged in normal operation.
One thing that is common sense to me but not to many people though: Lithium Ion batteries prone to heating up. The most important parts:
1) Don't leave your phone on the bed where it can be covered up and overheat. It may cause the fire.
2) Leave your phone on the hard surface that desirably not flammable. Stone or metal is the best. And leave the phone screen down, this way the battery surface most exposed to the air and will have less chance of overheating.
3) Take your phone out of its protective case. Protective case protects well in case of fall or impact, but it also thermally insulates the battery, This can cause the fire.
4) Keep your phone away from the heat sources like radiators, hot air outlets, and direct sun.
This is a short quick one, maybe I should make it a hub? What do you guys think?