I have in my home a Microsoft wireless keyboard which uses 3 AA batteries.
It transmits to a nearby receiver which is connected to a USB port on the
computer. When the keyboard was new, the batteries would last for 7 or 8
months. For some strange reason, I'm now changing them monthly.

Recently, I was away for a week and the system was completely shut down.
When I returned and booted up, the keyboard was lifeless. I tested the
batteries, and they tested completely and totally drained on my meter.
That's unusual, because they usually test just weak when I replace them.
So, while I was gone and the system was off, something drained the batteries
completely.

At first, I assumed it was the keyboard, so I replaced it with another one
of the same model, an older one that I still had on hand. Same result, one
month. Does this make sense to anyone? Thanks.