When to Replace Your Bike Helmet

Today I went to replace the brace in my bike helmet that had broken (for a second time). The first time I had it replaced the guy gave it to me for free. This time I was told, by people at the same store, that my helmet is too old and should be replaced.

According to the somewhat snooty mechanic who helped me a helmet should be replaced every three years because some of the plastics etc. break down. Now obviously the brace breaks down, but that's because it was poorly designed--too thin at the stress points--but the helmet itself is made out of fairly solid stuff, and has not been in any accidents.

I know the smell of horseshit, and in this instance it is the odor of a fresh dump. Clearly the call to replace a helmet every three years is brought on by the marketing departments of major manufacturers (Bell for instance). There should be no good reason that a modern helmet, designed to high standards, needs to be replaced just because of some arbitrary best before date, I mean c'mon.

I didn't tell the girl that she was feeding me a line of crap, but I looked around at the other Trek helmets and noticed that they still use the same kind of brace (although now it is a zip-trak version II), so they couldn't argue that the part was not available. I don't know what to do now. Do I cave and buy a new helmet, or stick to my principles and write a letter to the store owner and complain that his staff was selling me a line of BS. Actually, I know just what to do, I am the disclaimer after all.