If you are racing, make sure to buy an SA helmet, NOT an M rated helmet. SA is for racing, M is for motorcycles. If you get teched most track inspectors will not let you race with an M rated helmet. Check the rules of the tracks and sanctioning bodies you plan on racing at. Most will only allow up to five year old helmets, but some have a transition period after five years.
If you are in the market to buy a new helmet make sure to get an SA2010, and do not be suckered into a sweet deal on a "close-out" 2005 model for a few bucks less. You may only get to use that 2005 for another year or two...