I replaced a ~9 year old Giro helmet last year because the outer plastic shell was starting to bubble and come loose from the main foam shell, was never in a crash. I still trusted it to do its job, but it was getting pretty ugly and probably had lost some of its protective ability. Replaced it with another, very similar, new Giro... hope it lasts another 9 years without a crash! The only noticeable difference with the new helmet, is the clicky-wheel headband fit system, other than that it looks nearly identical to the 9-year-old model.