I had a Giro Pneumo, no crashes, no misuse. It developed a couple of cracks in the styrofoam material. Sadie Pate of Bell Sports took care of business and replaced the helmet with no shipping or handling charges. That’s standing behind their product and good customer support!
How old was it? I just bought a new Giro because mine had the same problem, but it was 3 years old. They said no warranty. I still bought another Giro though.
I don’t know how old my helmet was - but it had to be at least a couple of years old. On the inside of the helmet, it stated - life time warranty. I did have to send my helmet in. They checked it out to be sure it had not been abused. I did have to follow through with my e-mails and it took a few weeks to get everything accomplished. For a new helmet, well worth the time and effort