Youre a little coy about the real age of your helmet, but lets say its ten years old. If so, then I dont think your lack of an accident is due to the helmets talismanic value. I think its because your helmet is screaming, Whoa! Dont hit that rock! Or that one! Yikes!" as it frantically maneuvers your melon around obstacles in order to avoid its own demise due to its age-weakened state.
The thing is, even if the helmet looks OK, thats no indication of its structural integrity. Lots of things can decay the plastics and polymers in a helmet: sun (highly destructive), repeated wettings and dryings while boating, and your own sweat (very acidic) to name a few. Chances are the straps have lost half their original strength, while the shell may be far more brittle than it was when new. Bicycle helmetsa close kin to boating helmetsare thought to be due for replacement after three to five years, depending on how much use they get. I always err on the side of conservatism and dont let mine go more than three years.
Besides, buying a new helmet will hardly break your bank account. Pro-Tecs Ace Wake helmet (pro-tec.net), for instance, is only $60, and probably fits better and offers more protection than your old skull lid. And seeing as you have only one head, it seems prudent to invest in keeping it intact, no?
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