The answer to 'when to replace surge protector' is that you should replace your surge protector every 3-5 years, or if it has been damaged by a power surge. Surge protectors have a limited lifespan and can wear out over time, reducing their ability to protect your electronics. It's important to replace them regularly to ensure your devices are properly protected.
Over time, the internal components in a surge protector can degrade, making it less effective at blocking power surges and spikes. If your surge protector has been hit by a significant power surge, it may no longer be able to provide the level of protection it once did. Replacing it in these cases is recommended to avoid damage to your electronics.