I need some expert advice: I'm a photographer working on a late 2008 MBP 15" 2.4 upgraded to a 7200 HD and 4GB of RAM. The system performs well enough for my Photoshop needs, but I'm constantly dismayed by the battery life. My question for the you technocrats is the value of upgrading to this new customized machine, especially in terms of battery life: 15" 2.4 i5 w/ 500HD @ 7200 + 8GB Ram Would I see a significant increase in battery life from the old MBP or would the increased HD speed and RAM make the difference negligible? Ideally, I'd like to get at least five hours out of the machine on one charge. Thanks for your help.