You may be surprised by the answer.
There is a simple way to check – many helmets will have a sticker on the inside stating the date of manufacture. I remember buying mine “a couple of years ago” only to find it is coming up to 7 years old now.
How often you should change a helmet depends on a number of factors – and there are plenty of opinions on the internet if you chose to look. What is clear is that the science behind the design & manufacture of helmets progresses year on year so it is worth considering.
There are a number of different systems being used but Monica Weber reports that “other cyclists may be interested in the helmet I bought recently with a MIPS layer inside which stands for Multi-directional Impact Protection System. It’s made up of a thin layer of material incorporated into the inside of a helmet, independent of the helmet shell, but anchored at a few key points.
The MIPS technology allows the helmet to move around your head during a crash, meaning less force is transferred to the brain within.”
Certain companies are also offering discounts at the moment for trading in an old helmet for new so perhaps might be a good time to give your “bonce” a little extra protection.