Is this new Macbook unibody battery really new?

I have a 15-inch late 2008 unibody macbook pro, and I'm considering buying a new battery, (decided that I need 2 batteries, not 1). The battery at my local Apple store appears to be stocked 3 months ago. Will this battery still be 100% of its life even though it's aged 3 months?

And which is better, buying the battery online or purchasing through brick & mortar?