Surge protectors are easy to ignore, but they do not last forever. Most plug-in models rely on metal-oxide varistors (MOVs) to absorb excess voltage, and those components degrade with every surge — and even with normal use over time. A unit that has absorbed several spikes can stop protecting your equipment while still looking and functioning like a normal power strip.
To know whether a surge protector is still working, check its indicator light. Many models have a label such as "Protected" or "Protection Present," and an unlit light can mean the protection components have failed. If you cannot tell how old the unit is or whether it still offers protection, the safest move is to replace it. Also avoid plugging high-wattage devices like space heaters into a surge protector, since heavy loads can overheat the strip or speed up degradation.
Manufacturers often suggest replacing surge protectors every three to five years, but that is only a guideline. The actual lifespan depends on the design and the number and size of surges the unit has handled. Even a premium model may not last five years, especially in areas with frequent thunderstorms. And no standard surge protector can survive a direct lightning strike, so it should never be treated as a lightning shield. Mark the purchase date on a new unit and follow the manufacturer's instructions for its specific indicator lights.