The newer bulbs tend to last longer. The published life is based on a
minimum 4 hour burn time. The more you turn them on and off, the
quicker they'll burn out. But before everybody freaks out, you should
know that even if a bulb burns out 75% faster than advertised and you
don't recycle them properly, you STILL prevent more mecury from
getting into the environment--AND, you'll save enough money on
electricity charges to buy another CFL and still have change left
over. The electricity to burn a standard incandescent bulb (from a
coal fired plant) pollutes almost twice as much.