From some NiMh VS LiPo forum I read,
The Lipo must keep in 40% of its total charge capacity to ensure life expectancy. It could last for very long time and takes many cycles without degrading in a well control environment.
Over Charge or Over Discharge LiPo overheats the Lipo cell, is also dangerous. The Heat damages the cell and shorten its Life Expectancy greatly. Many LiPo reaches it's point which are no longer safe to use. !!It can Really Blow your RC into pieces!! Those Extreme Heats it can produce can even catch metal into fire. check out youtube for lipo.
Lipo cell are fragile, it needs protection in High G Environment. An internal shortage of a damaged cell could cause Heat and destroy your RC car completely!
We are still in the drak age of LiPo. Higher output cell, the more active chemistry, the high risk. Be a Wise Careful person when using LiPo.