mid 2009 macbook pro battery life

I have a mid 2009 13 inch Macbook pro (model 5,5), 8gb RAM, hard drive has been replaced with a 500GB one. Last year I replaced the battery (genuine apple purchased from an apple service centre). Staright after installation I was only getting 2, 2.5 hrs from the battery. The service centre replaced the battery with a new one, same story. I have reset the PRAM, SMC, calibrated the battery, and have done all of the usual power saving tricks. According to Coconut battery the battery is health is good and I am getting full charge. After resetting the PRAM and SMC (again) I am now only getting an hour from the battery. Any ideas as to what the issue may be? The laptop runs perfectly well, it's just the battery life that is the issue.