When you use the Lipo battery you should be very careful while charging it.  You should follow the instructions very carefully for a long life battery.  Basically the charge should be done at a constant current of 1C to 2C, depending on the manufacture, till each cell reaches 4.2V. 

While charging the charger should not be terminated as soon as the cell voltage of 4.2V is reached because at this point you have charged your battery only to 70%.  If you stop at this point the charge does not stay for long and it may result in loss of charge very soon.

It should be noted that charging should be done at one time till the end, if it is interrupted before reaching its full charge it may cause damage to the cell probably plating out the lithium metal and thus making it unsafe. 

If you would ask the advice of a manufacturer they would suggest something like a maximum voltage of 4.23 and a minimum of 3.0 volts per cell. 

 

Mostly all lithium polymer chargers make use of a timer to charge safely.  This automatically cuts the charge at a predefined time of approximately 90 minutes.  This is highly recommended in the interest of the life of the battery.  Surely no one would want to have a battery that breaks down quicker than expected.  If they are used according to specifications surely these batteries would serve the purpose beyond your expectations.