That's beginning to sound like an application is running on the device and not letting it go into standby mode. Have you tried a soft reset? If not, maybe a hard reset/re-install will clear it.
The fact that you've had it for 2 years and now all-of-a-sudden it's draining batteries definitely suggests that something is running on the machine that is preventing it from hibernating. That rate-of-drain of the battery is about what you would see if you were playing a game on it for a couple of hours or something. Make sure all programs are shut down and see if the problem persists.
-CB
