Charging all night and its effect on the charger
Failure of electronic components can be caused by a range of different mechanisms, but the common factors that accelerate failure are heat, applied voltage and applied current.

If your charger is well designed, and stays cool, and your mains doesn't suffer from large voltage spikes, then I wouldn't expect it to fail from staying plugged in - at least not within the expected lifetime of the device it was intended to charge. If the charger is allowed to continually get hot because of poor ventilation, or if it's badly designed or cheaply made such that one or more components are operated close to or outside their voltage, current or power handling capabilities, then I guess unplugging it when not in use might extend its lifespan.

There are some failure mechanisms that arise from thermal cycling, i.e. alternate heating up and cooling down, which might argue for leaving the charger powered, but it'll probably undergo thermal cycling anyway because it will heat up when charging a device and cool down again when idle.

(Some background information on failure mechanisms of electrolytic capacitors and semiconductors, which I would guess are the most failure-prone non-mechanical parts of a switch-mode charger circuit.)