TIP #1: KNOW EXACTLY HOW AND WHEN TO CHARGE YOUR BATTERY
Charging is the Key to extend the battery's lifespan. For getting the best flight time possible, charge your UAV battery right before you're about to use it. "Freshly" charged batteries usually perform better than ones charged several days beforehand. Besides, when you are not about to fly, charge it only 60% of the way and store it in a safe place instead of fully charge it. And, NEVER OVERCHARGE. If the batteries are charging overly, they may ignite or even explode. It is dangerous and also detrimental to the battery's lifespan.
TIP #2: DON'T ALLOW YOUR BATTERY TO COMPLETELY DRAIN ITSELF
Each time that you do this, you slowly wear down the lifespan of the battery. It is recommended that you fly your quad copter with no less than 3.5V. Once it dips to 3.5V, stop flying and give the battery a rest, then charge it for use next time.
TIP #3: AVOID THE STRONG WIND
When you fly your quadcopter in strong wind, your motors have to produce more thrust to maintain the flight, which requires more power conducted by batteries. Therefore, it is highly recommended to fly in a good weather or low wind.
TIP #4: CHOOSE A CONSERVATIVE FLIGHT MODE
Nearly all RC drones come with various "Flight Modes" that you can switch by simply putting a button. The aggressive mode increases transmitter sensitivity and consume more electricity. Conversely, flying more conservatively consumes the power more slowly with a lower sensitivity. Try to fly conservatively when you are not racing!
TIP #5: LIGHTENING YOUR EQUIPMENT
Since the battery discharges faster while recording and shooting, you can turn on the camera and even remove the camera (if it is detachable) to slow down the pace of discharging. This may be helpful of prolong the battery's lifespan.
TIP #6: BUY EXTRA BATTERIES!
The flyers are now purchasing more batteries, for use or for backup, to maintain a long flight time for their drone. Generally, spare batteries can be accessible easily and can be purchased on sites like:
genstattu.com
These tips can make sense in extending the battery's lifetime, but it is unrealistic to double the flight time. SO, taking good care of the batteries and using it properly.