Fluorescent lights have a life rating based on how many hours they are left on every time they are turned on. Every time a fluorescent light is turned on, a tiny amount of the coating on the electrodes is burned off. Eventually, enough coating is burned off, and the lamp fails to start. Most full-size fluorescent lamps are rated to last 20,000 hours when left on for 3 hours every time they are turned on. This means that the lamp has roughly 6,667 starts available to use up.
Longer burns extend lamp life.
However, you are paying energy costs for the operating time of the lamps, and the most efficient lamp is the one that is not on when it is not needed. See Table 2 for the effects of longer burn time on lamp life. But longer burns use more energy. Operating a light when it is not needed is simply spending money for no purpose. Today's rapidly rising electric rates mandate that every building becomes leaner with energy use to control costs.