Is it normal to be able to hear a high pitch buzz from devices that are charging?
50Hz is really low audio frequency. High pitch noise (above 10kHz usually) is coming from cheap switching power supplies. Normally designers try to use higher frequencies (outside audio range) to avoid this annoyance or mechanically dampen it (e.g. gluing), but cheap supply designers... well, don't care. Here is wiki article about it.

As for lifespan - any kind of vibration affects mechanical durability. In this case you probably have higher chances of some other cheap component crapping out long before mechanical fatigue affects anything else.