my MacBook Pro battery life is terrible – is it defective?

My MacBook Pro is 18 months old, and the battery life has degraded terribly. I originally got three to three-and-a-half hours out of it. That wasn’t anywhere near the seven hours Apple advertised for the new built-in batteries. But it was way better than the two hours I got from my previous MacBook Pro, so I was reasonably happy. However, now it burns through the battery from 100% down to 5% (when it goes to sleep) in about an hour.

I downloaded the latest version of coconutBattery (2.8) to peek into what’s up with my battery. I’m sad to say that it’s reporting the current capacity to be 2977 mAh out of a design capacity of 6900 mAh. No wonder it seems like my battery lasts less than half as long as it used it. In the 18 months since the Mac (MacBookPro8,2) was manufactured, it has had 297 battery load cycles.

Looking at Apple’s published information about the battery, I found this:

Your new Apple notebook features advanced battery chemistry that greatly extends the battery’s lifespan. The built-in battery of your MacBook Pro or MacBook Air is designed to deliver up to 1000 full charge and discharge cycles before it reaches 80 percent of its original capacity. In addition, Adaptive Charging reduces the wear and tear on the battery giving it a lifespan of up to 5 years.

So Apple says the battery should degrade to no less than 80% of original capacity until 1000 cycles. But I’m down to 43% capacity after only 297 cycles. Do you have any suggestions how I should handle this? The one year warranty has obviously expired.