John Kernan wrote:
What should it be? The store says seven hours, and while I'm not naive enought to believe that, still my new MBS says it will ge about 2.25 hours with power set at "Conservative." And it sems to be going down faster than that.
The store does not say "seven hours." Apple says "up to seven hours wireless web."
Those bold words are very important. No matter what device or what brand you are talking about, battery life always depends on how much your specific group of programs is stressing the battery.
Apple tells you what they mean by "wireless web" usage. It says at the bottom of the Tech Specs page:
Testing conducted by Apple in September 2012 using preproduction 2.5GHz dual-core Intel Core i5-based 13-inch MacBook Pro units. The wireless web test measures battery life by wirelessly browsing 25 popular websites with display brightness set to 50%. The standby test measures battery life by allowing a system, connected to a wireless network, to enter standby mode with Safari and Mail applications launched and all system settings left at default.
Now read that carefully. Are you using the model they listed first? If not, you adjust your expectations based on the CPU and battery size for your model. Now read "The wireless web test measures..." Apple is giving us a baseline for expectations there. Do your own activities and configuration impact the battery more or less than those Apple lists? Is your monitor at the same brightness level? If more, you lower your expectation of the run time. If less, you raise your expected run time.
For example: If you are using your MacBook Pro to run special-effects software with a Bluetooth control surface to render video, with the monitor at 100% brightness, while downloading big files, chances are your battery will last less than 2 hours, because those activities will make the radios, CPU, and disk consume power at a high rate, draining the battery quickly. But if you are on an airplane, which requires you to turn off wifi and Bluetooth so that you have no radios running, and where you will probably turn down the backlight in a darkened cabin, and all you are doing is writing text documents so that the CPU and disk are not doing much work, there is a very good chance you will exceed 7 or 8 hours on battery because the power drain from all components is light.
I've had my MacBook Pro for about 9 months and I still see it say 6+ hours sometimes, but mostly I expect 3-4 hours when doing typical work. Which makes sense because that work is more demanding than Apple's test.
There is a 198 page thread discussing lower battery life and drops in battery health on ML which you'll find here: https://discussions.apple.com/thread/4135250?start=0&tstart=0 . If you think you have a problem, the best thing you cna do is take it to an Apple store and get it checked out. If you really do have a battery issue, then also provide feedback to apple at www.apple.com/feedback.