Many already know this, but on the Tour, if you press and hold the mute button for about a second, the device goes into "Standby Mode."
I haven't been able to find definitive info on exactly what standby does beyond shutting off the backlight and standby locking the keyboard, but the phone and alerts still ring, so no worries about that.
The point of this post: anecdotally, it seems to improve battery life.
Since it locks the keyboard too, I'm trying to train myself to use this instead of hitting "K."