All servo's no matter what brand fail in time .

As for HV servo's they are more related to helicopters than cars .

Hv's relate to the motor of the servo not the electronics as most electronics can handle up to 9 vcc especially digital servo's

From what i know and have studied real HV's servo's are 49mm in height and don't fit in car's anyway .You will see in time that the ones who claim to be HV's are not HV's at all but can tolerate the voltage for some time until the heat and current finally kills the motor .They might last 1 minute to 1 year who knows.

just my two cents worth