A lithium battery

A lithium battery prefers a partial rather than a full discharge and frequent full discharges should be avoided when possible. Instead, charge the battery more often (they are good for 300-500 discharge/charge cycles) or use a larger battery. There is no concern of memory when applying unscheduled charges.
Aging of lithium-ion is an issue that is often ignored and a lithium battery has a lifetime of 2-3 years. The clock starts ticking as soon as the battery comes off the manufacturing line and the capacity loss is the result of increased internal resistance caused by oxidation. Eventually, the cell resistance will reach a point where the pack can no longer deliver the stored energy, although the battery may still contain ample charge.
With lithium cells, there is always the risk of fire which can result from shorting, improper charging or crash damage to the batteries. And because a lithium battery fire is very hot it often starts other fires which can result in burning down the house!
Now the reason fire occurs is due to contact between the lithium and oxygen in the air. It doesnt need any other source of ignition or fuel to start, and burns almost explosively.