I say remove whistle-call.
Cavalry pretty much has two lives in certain instances, and the whistle-call only makes it so they can go back to full power and get a third life and repeat and repeat and repeat until THEY are personally dead with the click of 3 buttons.
you arent correct, if all cav have two lives, there will be no free horses on battlefield to "get a third life and repeat and repeat and repeat until THEY are personally dead with the click of 3 buttons."
So these third-fourth lives are only for skilled cav, who not only live longer when other cavalry to find free horses, but also survived long enough on foot to go away from enemies who unmounted him and only then take that horse.