Probably not. The CPSC standard for bike helmets in the US took effect in '99 and hasn't changed since then. The only test I've seen on an older helmet was of a 10 year old well-used Bell Biker and the report showed it did just as well as new ones had when first tested. There may be an advantage if you go for one of the few models that now market the MIPS technology - not clear how much difference this will make in real-world accident data. (My helmets are currently 39 and 21 years old and I have no plans to replace them.)