The lifespan of a riding helmet is five years from the date of first wear. Even if you haven't been in an accident with your helmet, it's important to replace it after this time. This is due to natural wear and tear on the materials. If your helmet suffers any kind of impact, no matter how small, its protective qualities will be compromised. You should replace your helmet before riding again. Lastly, if your helmet ever becomes too loose or too tight, it's time for a new one.