Any Helmet Needs to be Replaced in every 3 years.

The most important part of a helmet is an expanded polystyrene (EPS) foam liner (which resembles Styrofoam) That is like those white packing box material when you buy a TV from Walmart. This EPS actually absorbs the energy of an impact. DOT standard requires 1 inch thickness of it.

In a crash, the polystyrene is permanently crushed, so if you hit your head with your motorcycle helmet on, the helmet is no more use to you than a baseball cap. The helmet may look just fine externally, perhaps just a small scratch, but it probably no longer has impact-absorption in that area. The important points that a motorcycle helmet should protect, according to the Snell institute, are the crown of your head, your temples particularly right behind your eye socket, and your jaw.

Your helmet should be replaced every 3 years. This makes sense when you understand that plastic foams do break down over time, just from exposure to sunlight. So make sure you replace you helmet on that timescale and more frequently. It is very simple to say. You get the white packing foam after you buy a TV and put it aside for 3 years in your garage. See how fragile it can become.