The answer to 'how long does surge protector last' is that a quality surge protector can last 3 to 5 years with normal use. Surge protectors contain components that wear out over time, like the MOV (metal oxide varistor) that diverts excess voltage. As these components degrade, the surge protector becomes less effective at protecting your electronics.
It's a good idea to replace your surge protector every 3-5 years, or if you notice any signs of damage like scorch marks or a tripped breaker. Surge protectors are an inexpensive way to safeguard your valuable electronics, so it's worth investing in a new one periodically.