That depends on what formula is used. Some use 24 hours a day, seven days a week, while others use 12 hours a day or even six hours a day (based on use between 5 and 11 p.m.).
These guidelines don’t work for me, though. I get home at 6 p.m., drink dinner, fall asleep on the sofa until 11 p.m., when I wake up in total darkness and then shop online until 2 a.m. So my LEDs will definitely outlive me.