Well, I’ve had my Magic Mouse for less than a month and yesterday I got an error message warning me that my (2) AA mouse batteries were low. By the evening, the Bluetooth mouse stopped working due to dead batteries. They included Energizer AA alkalines from the factory. Let’s hope a fresh set will last longer this time!
On average, I use my Mac about 8 hours a day and do not turn the mouse off when I’m done using it.
Update Jan. 4, 2010: my set of Energizer AA rechargeable batteries lasted 34 days this cycle. I recommend everyone using the Magic Mouse keeps a spare set of AAs around for a backup (or a wired mouse).
For all of my AA needs, I use Energizer nickel metal hydride batteries (NiMH) that I got for $8 on sale, but there are many good options available here: rechargable AA batteries from Amazon.com. Use the customer star ratings as well as cost to aid your decision. NiMH rechargeable batteries easily outperform alkaline batteries so pick up a set and you’ll save a ton of money in the long run. Strobist has an excellent article on rechargeable AA batteries on their blog.