Yes, 80% is a critical point in lithium polymer/Li Ion cells, the cycle life is drastically reduced after that point. In fact, the less DOD (depth of discharge) you go, the longer they will last. Exponentially.
“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens