My old MBA is running out of disc space and after 800 cycles the battery only lasts a few hours. So I appropriated my wife's when she upgraded to a 12" Macbook. However, I'm getting really weird battery life issues. When I tried it with her stuff still on it, it would show 5-6 hours or so on a full charge (it has 250 cycles). But when I wiped the hard drive, reinstalled OS X and migrated my stuff, that dropped to 3 hours. About the same as my old MBA. So I wiped it gain and reinstalled OS X and didn't migrate my stuff. Now I got 7-8 hours. Then I migrated my stuff (apps and user ID) and it went back down to 3 hours. I thought it might be Spotlight indexing, but after waiting for that to finish there was no improvement. So I wiped it again, reinstalled OS X, did not migrate anything, and just for the heck of it blocked Spotlight from seeing the hard drive. Now the counter is showing 12.30 hours of battery life. 3 hours to 12 hours is a massive difference. Any thoughts what might cause this?