I crashed in a 10 year old Giro Interceptor helmet last year. Only cracked my skull in three places.
So it worked and saved me. Would I have fared better in a new one? Who knows? But since I now know that I'm not indestructible as I thought for over 60 years, I'm going to replace my helmets every few years.
Hopefully it'll be another 60 years till my next helmet test. <grin>