Just to further the Snell vs DOT discussion:
The Snell Memorial Foundation (SMF) is a not-for-profit organization created to provide a high quality standard of safety for helmets. Founded in 1957, SMF is named after William "Pete" Snell, a popular sports car racer who died in 1956 of head injuries he received when the racing helmet he wore failed to protect his head. A group of friends, scientists, physicians, and others joined together to create a group that would promote research and education as well as test and develop standards to improve the effectiveness of helmets. Snell Standards significantly surpass those set by the U.S. Department of Transportation (DOT), the American National Standards Institute (ANSI), ASTM International (ASTM) and the U.S. Consumer Products Safety Commission's 16 CFR Part 1203. Snell Standards are updated about every five years. These updates are based on new scientific research and improved, available manufacturing technologies. As such, and in addition to other factors such as typical use wear and tear, Snell recommends that helmets be replaced approximately every five years to ensure good safety.
As far as the styrofoam degradation issue goes try this. Take a cooler from any mini mart and store it in your garage for a couple of years. Expose it to sunlight one day a month. Tell me how well it works when that time's up.
My experience here in Alabama is two years is the max for unprotected styrofoam, the stuff crumbles like dust after that; I suspect 5 years is good for the stuff in my brain pot. You city folks may be exposed to more ozone so there's no telling how long it's effective in your dense urban areas. I know this, $20 a year ain't much to protect the ol' noggin so I'll be getting a new Bell RT every third year. (they get pretty smelly after that)
