Replace all batteries at the same time. Do not mix old and new batteries. Use batteries from the same brand, type and expiry date too.

Use batteries for their right purpose: insert them correctly, replace them when empty and store them dry and at room temperature.

Yes. All batteries have an expiration date, beyond which their performance decreases.

A battery is a chemical product which produces electricity by chemical reactions at its inside. These reactions and its inside materials do deteriorate over time. If you start using it within that period, the battery will operate normally and maintain the specified performance.

Do not throw batteries in the trash. You can recycle every battery type you use - even unusable rechargeable batteries. Recycling points and regulations are different in every country.

Battery leakage is caused by forcefully discharging, short-circuiting, or the safety valve releasing excess gas from inside the cell.

In general, appliances are designed to match the characteristics of dry batteries and to work within the voltage range of 1.5V to 0.9V. Thanks to this characteristic, Ni-MH rechargeable batteries can be used in appliances which require alkaline batteries, even with lower initial voltage. 

Battery performance greatly depends on the device and on the conditions.

As new energy flows into your battery, some heat is perfectly fine. If you notice the battery or charger becomes too hot to touch, cease the charging process immediately.

No. Do not use batteries in water or in vacuum conditions - this will cause them to rust and short-circuit.