You need to find out your current capabilities, and then be training for improvement. A shot timer is more about tracking improvement than setting a magical par time. What would you do when you reach that goal? Say "good enough" and move to something else?
Find out your average for whatever task you are looking to improve. Set the par time for .2 less than your average, and as you start beating the par time, decrease that par by another .2. You will train for continual improvement this way.