I have the Apple BT keyboard, been using it for about half a year. I put in a fresh set of batteries about 3 months ago. It remained at 100% the whole time but in the past couple of weeks, it's drained exceedingly quick. I usually turn it off when I'm not using it. When I turn it back on, it's somewhere around 40~50%. Along the course of the day, it slowly drains till ~15%. Sometimes it cuts off. Is this typical behaviour? I know batteries restore their charge when left unused, but 20% -> 50% is quite a huge variation.