The answer to 'when to replace surge protection' is that surge protectors should be replaced every 3-5 years, or sooner if they have protected against a major power surge. Surge protectors wear out over time and can lose their ability to effectively shield your electronics from power spikes and surges.
It's important to regularly inspect your surge protectors for any visible damage or degradation, and replace them if they are no longer functioning properly. Signs that a surge protector needs to be replaced include a lack of indicator lights, physical damage, or if it has been used to protect against a significant power surge or lightning strike.