What is the recommended replacement lifespan for a motorcycle helmet under normal riding conditions without prior crash impacts?

1. 15 to 20 years, provided the helmet is stored in a cool garage between rides
2. 3 to 5 years from the date of regular use, due to degradation of interior resins, EPS foam aging, and ultraviolet (UV) exposure
3. Helmets never degrade and remain fully effective throughout the owner's lifetime
4. 6 months, regardless of usage frequency or manufacturing materials