LIPO batteries can become unstable at low voltages. If you leave it plugged in, the voltage will slowly decrease, potentially resulting in a battery fire. Burning your house down is not worth the few seconds it takes to pull the battery. Similarly, balance charging is critical to prevent the cell voltages from drifting too far apart and also creating a stability issue / fire risk. Most battery fires seem to happen due to physical damage, leaving them in vehicles plugged in for long periods, or charging mishaps.

Primary rules of LiPO safety:
1. Always unplug the battery when not in use
2. Always balance charge
3. Store the battery safely
4. Don’t charge while unattended