What's the commercial? Would you have a link? I wonder if you actually heard "daily use". We could help you a lot more easily if we knew what the product was.

These phrases really just mean exactly what the two words of each phrase mean; "day use" means something you use during the day, and "ongoing use" means something you use for a longer but unspecified amount of time. Also occasionally "day use" can mean something which you use for only a single day, but that meaning is less common. "The car has no headlights so it is for day use only. " - Only use the car during the day. "We purchased a day use pass to get into the park." - A pass allows for a single day of visiting the park. "Some people choose to experiment with illegal drugs, but ongoing use can have serious side effects." - Use of drugs for a long but unspecified amount of time.