A helmet should be replaced when it is no longer in a condition to be able to do its primary job, helping keeping its owner safe in the event on an impact. Inspect your helmet regularly for the following: Outer polycarbonate shell is cracked or separating from helmet foam Helmet foam is dented, compressed or otherwise damaged Straps are fraying Buckle or fit system is cracked, broken or no longer operating correctly Fit system is no longer fixed to the helmet shell On MIPS equipped helmets, any of the tabs holding the MIPS system in place are no longer fixed to the helmet shell All of the above are signs that the helmet should be replaced as soon as possible