It's never let me down.

[BluesDave]

I've had my (cycle) helmet for over 12 years and it's never let me down. Not that I've been involved in an accident where it could.
I only discovered last week that I could wash the fabric bits in it as they are stuck on with velcro thanks to another post on here.
How long have you had yours?

 

[HLaB]

Its probably a marketing tool but you are supposed to change them every so often; I dare say that mine is older than that (no idea the actual age) but I only really wear it to shut up the safety nannies and reassure those close to me.

 

[sdr gb]

I think its advised that they should be replaced after 5 years at the most. I've had my Giro Monza for 5 years now and don't intend to replace it any time soon.