It is a good idea for two reasons. The zinc alloy will reach operating temperature faster, because the heating element doesn’t have to heat up the mass of ingot which solidified in the melt pot. Also, as the alloy solidifies, it shrinks, and the ingot puts strain on the ingot feeder. While the ingot feeder is a strong component, with a spring built into the hook to compensate for the strain, the few seconds it takes to lift the ingot out of the alloy will add to its longevity. It also makes it possible to remove the pot covers while the pot is still frozen.