Reader Tom writes:

Marketing guy 1: "Hey how about this for a slogan... 24 Hour Protection?"
Marketing guy 2: "Yeah, that's great! Let's put it on our bottle!"
Marketing guy 1: "Wait, if we say that, the consumers will only use it once per day and we'll only sell half the volume!"
Marketing guy 2: "True... so let's be sure to remind them to use it 2x a day."
Marketing guy 1: "Cool. We'll put both on the label. 24 Hour Protection that you use twice a day. Oh, and we'll clarify by putting Use Every 12 Hours, just in case they get confused."
Marketing guy 2: "Yeah, that makes perfect sense."