For me it depends on price. If I am paying full price, I expect <six months old. If you want to sell me a helmet four years old and new in box, I'm not interested unless price is <20% of msrp. I don't care that it's new, it's most of the way to aging out. In practice, that means I very rarely buy aged helmets as most sellers hold out for someone that either doesn't know about age or is willing to accept an old helmet for a small discount.