I was told by my bike shop that it's sweat that breaks down the foam the most. If the helmet hasn't been used, it probably hasn't degraded much at all.

Also, I had a Giro Pneumo that really saved me during a crash in May. While the outside of the helmet wasn't even cracked and you had to really search to find where it contacted the ground, the foam on the inside cracked down the middle. There was absolutely no damage to my head. Then I got to take a sledge hammer to it at the bike shop (I guess they can't just put it in the dumpster when it had been through a crash) and it took 4 good wacks before I broke the plastic. I highly recommend that helmet!

Susie