I guess I am not understanding the N800's concept of "idle" or I'm doing something wrong.

How do I make the N800 enter "idle" mode. I've read a lot of threads on screen locking, is that idle? In the battery status it shows idle time on a full charge as 8 days (down from 10, how did I loose 2 days already, it is only 2 days old.) When I "Lock touch screen and keys" and let it sleep (after a minute, the screen will turn off and not respond unless I push power button, as expected) if I check back two hours later, the idle time is down to 5 days. If I lock it again and check back in an hour, the idle time is down to 2 hours. Basically it looks like I'll get maybe 8 hours of idle time.

Thank you