Wow...
I don't want to get into the "works" of the DOT law that came out and started forcing "life limits" on helmets, which was intended for drag racing applications after a politically-connected NHRA racer and helmet manufacturer's son got hurt (head injury) after a big crash, but....helmets do not wear out on their own. They wear if they hit something solid with something heavy inside of them (like you), and after a crash, should be replaced.
Politics and litigation being what it has become in this country lately, this "life limit" on helmets was trumped up by several New York lawyers who got big $$ from the afore-mentioned party's company, to lobby the new DOT bill through Congress and ram it down our (and other's) throats. The helmet manufacturer, whom I will not name, but is an acquaintence, is a multi-millionaire as the direct result of this 'coup'.
I'm not going to discuss the age of my like-new helmets, either, all of which are Snell-approved: there have not been but 3% improvement in deceleration physics in these helmets since the NYC Z90.1 spec of 1972 became national law. It is outrageous to force anyone to replace perfectly good helmets with something less, which most of today's offerings are, than a 1970 Snell-rated skid lid. Only the $500 modern full-coverage roadrace-rated buckets are slightly (2%-5%) better, today, and this much difference will not make a helmet 'safer'. Try to find a 5-layer, fiberglass, hand-laid, cooked and tested shell with a 30-year rated adhesive life today for less than $700: impossible. They are all cast polycarbonate shells of one type or another, usable once, and can be damaged by falling off the bike seat to the concrete. The last hand-laid ones offered were from ARAI in 1986. No one makes any better than those were, today.
But they do cost a huge amount more than those did. I don't trust most of today's helmets: I've seen their test specs. The Snell foundation awards their label (if indeed they even still do) to the best of the year's crop, not necessarily the ones that were better than last year's group. The influx (and infection) of cheap goods from China and other similar operations recently has muddied the waters even more, now. I just had this discussion with a lawyer who was pulled over last year on his bike for some minor thing, and got a ticket for an "expired helmet sticker". His helmet was 6 years old at the time, and was used maybe 10 times as he usually wears his [older] open-faced one: this was his newer full-faced one. To call that helmet 'out-of-date' somehow is so ludicrous as to be a crime, perpetrated on us, the People.
Yes, I used to get crosswise with The Fuzz in the 1960s...I also have a Law Degree and a BS in Police Sciences, along with my Engineering degree....and lately, feel some of that '60s ire coming back to life, over stuff like this...

P.S....if anyone knows where I might find a hand-laid, fiberglass or Kevlar multi-direction-weave, multi-layered lid with at least 180 degrees of peripheral vision (I have 178 degrees of it) and weighs less than 2.5 pounds and costs less than $500, I'd like to hear of it...
(Rant over.)