Curious to know what others think about the general recommendation to replace your helmet every five years. Can understand that helmet manufacturers recommend this for obvious $$$$ reasons but you'll see this advice from motorcycle safety foundations too, and they wouldn't have any direct financial interest in seeing more helmets sold. There's so many variables involved -- seems like the key thing here is miles ridden versus age of helmet sitting on a shelf. In fact, who knows how long a helmet has been in a store before you buy it, which makes the five-year rule of thumb kind of a crap shoot. Any thoughts out there on this?