I have had my iMac for about 3 months now, and have changed the batteries on the mouse already once. Now the Keyboard, Tablet and Mouse are all complaining with less than 15% charge in each of them. They all orginally came with the Energizer Lithium batteries. The mouse lasted about 9 weeks with them. I replaced the mouse with regular energizers and it has stood up for about 6 weeks. The keyboard and tablet (that doesn't get much use) have lasted about 13 weeks. What is standard for these wireless devices? What sort of battery is the best bang for the buck?