-Hi there, I have a question about helmets. I recently bought an Arai helmet from a local dealer. It's a new helmet, but and old design, a 2003 model I was told.

Apparently, the dealer found it when he was moving a load of stuff around his premises. He let me have it cheap. Honestly, I couldn't be happier with it; the fit is perfect and it looks great.

My question is to do with its life pan. On the chin strap, it says to change the lid either seven years from manufacture, or within five years of first use. My worry is that the seven years is up in two years; surely, as I only wear it at the weekends, I could get a bit more years out of it. What do you think?

It is simple, ignore the seven years rule and stick mainly to the advice stating five years' use from first use. It also depends on the amount you use the helmet, though. A motorcycle messenger would have to change lids far more often than your average weekend rider.

With the Aria helmet, it's also possible to replace the lining and cheek pads to prolong the helmet's life. With changing the pads every now and then it will feel like new.

It's probably not advisable to let a helmet do the amount of kilometers some people do, but then, some people reckon that they not need much protection. So I want to say people change your helmet every 5 years after first use...

How much does helmet weight vary from brand to brand? I'm interested in a high-quality helmet but would like to get the lightest one. How much do the Arai and Shoei helmets weigh?

The weight of a helmet varies with its size and graphics package. A plain white helmet can weigh several grams less than a helmet with graphics. My g/f has a Aria helmet and it weighs 1350 grams, what is about the average for most helmets. Some are 100 grams heavier and others are 100 grams less weight...

So long as the helmet wasn't stored near any volatile fumes that could eat the foam away or left in the sun (UV) all this time, you pretty much have a new helmet.
Sounds like you got a great deal.
I've seen some carbon fiber helmets out, but they have so much clearcoat they may be heavier than the plastic ones.