While this can be useful to discharge battery completely just for
calibration of battery monitoring unit, it serves no purpose to
"deep-cycle" battery everytime, since it wears out on battery
more than charging it when it's still partially charged (it's like
expanding a spring, it wears out less when you expand it more
frequently, but to lesser extend, than when you force it to expand
to it's limits but less frequently)... I've proved this to myself with
my previous phone (SE P900, with excellent battery, Li-Pol 1260mAh
and 16h of talk time), when I've killed first battery by NiMH "care"
method (discharging completely until phone won't boot + fully
charging) in about one year, while next one used in normal way (frequent
charging when not completely drained) served me for about 2.5 year...