There’s technically no reason you can’t always leave your countertop ice maker on, though it’s not the best idea for several reasons. For one, these ice makers are not designed to keep ice cold for a long time, and eventually, the ice will melt and drain back into the water reservoir. Leaving your countertop ice maker on all the time will also decrease the overall lifespan and use unnecessary electricity. So it’s best only to turn it on when actively in use.