Most manufacturers recommend replacing a motorcycle helmet every five to seven years even without a crash, since the internal materials that absorb impact degrade slowly with heat, sweat and UV exposure. The shell can look fine while the protective layer underneath has already lost some of its effectiveness.
ECE 22.06 is the current European standard that motorcycle helmets are tested against, and it replaced the older ECE 22.05 standard with a wider and more demanding set of tests. Helmets are checked for impact absorption at multiple points on the shell, not just the crown, and the standard also tests rotational forces, which earlier standards largely ignored.
For helmet care products and guidance, see
Hedonist.
A helmet is the most visible piece of riding gear, but it works as part of a wider kit rather than on its own. Gloves protect hands in a low speed drop, which is one of the most common types of fall, and a good pair balances grip and feel with real abrasion resistance.
The liner deserves the same care. A removable, washable liner keeps the inside fresh, and following the maker's washing instructions protects both the padding and the stitching around it.
Full face and open face helmets suit different kinds of riding, and the right choice usually comes down to where and how you ride rather than looks alone. A full face helmet covers the chin and jaw, giving more protection in a wider range of impacts, and tends to suit faster roads and longer distances.