It helps conserve moisture and keep weeds down but it’s possible to spread too much mulch. (Find out the dangers of layering it too thick — or too thin — in the chart at left.)
If you really want a fresh look, don’t just top mulch off. Use a rake or fork to fluff the surface a little, which can help brighten the bed. Or simply rake away some of the old material and use it in less visible areas or add it to your compost pile before you put down new.