There is no fixed relationship. The quantity that relates energy Transfer to Time is Power (Watts are Joules per second) and a device can have any power the designers choose, the only limit is practicability.How much time does it take to convert one form of energy to another.
Half way down half of the PE has been converted to KE. When it hits the ground all of the PE will have been converted to KE. You can use the equations of motion to calculate how long it takes to hit the ground.How much time does it take to convert one form of energy to another. Say ball dropped from a height 'H' its PE convert to KE. Can it be be defined in a time frame?