I'm not sure how much water a typical cleansing will require; our cold-water one is on its way to the house now. But I reasoned it would probably not require more than a 1-2 second blast.

Given that it's plumbed in at the toilet tap, and that you'd use it before flushing, I would presume the water would be relatively close to room temperature, as the supply line is indoors just below the seat. That should be plenty for 1-2 seconds.