My magic mouse is several years old; it came with my 5k imac. For the lifetime of the mouse I've been replacing the double A on a weekly basis. I've been using rechargeable duracells. Some days ago I got fed up and decided to go for some eneloops-- figuring that constant charge cycles had worn down the duracells (which have been derided as bargain basement anyway). But after a couple of days with the eneloops, I'm already down to 44 percent. Is this normal? Is there a firmware update for this mouse? Or is this just a fact of life?