It’s often recommended that a helmet worn frequently should be replaced every 3 years or so. The reason is that the foam degrades due to sun, heat, salty sweat and other environmental factors, added to the usual knocks of regular cycling activity.
These things make the foam unable to provide the full protection it’s designed for in the event of a head impact. A helmet should certainly be replaced after it’s damaged in a crash or even dropped hard.
However, some experts (presumably those not working for helmet companies) maintain that a helmet will be protective no matter what its age as long as it’s undamaged. In their view, there is no age limit.
There’s no arguing, though, that buying a new helmet every 3 years will keep you current with comfort and safety features as well as style. It’s remarkable the improvements we’ve seen in helmet lightness, ventilation and fit. And now, of course, MIPS and other “concussion-mitigation” helmet technology is available as well.
Many newer models have a “cradle” for the lower rear of the head. This makes them more stable on bumps and rough roads. And some feature a full “halo” fitting system that encircles the head, vs. just pulling the helmet from back to front to snug it against your forehead.
Typically, you pay more for a wider array of features, as with most all cycling gear. But there are many, many fine choices at the lower and mid-range of the spectrum, too.
You can find big savings on this year’s helmets when next year’s are introduced. Check bike shops and online, find the price and style you like, then wear your helmet on every ride you take. No exceptions.