Boy I was typing fast... look at those typos!!!!
Sorry if my response was confusing... let me clarify:
Do all recent BB's have the sleep function - Yes.
Since this thread was started in relationship to the 7100 I was answering in that context - the 7100 screen shuts off after a set amount of time (backlight and pixels). In or out of the holster.
The 7200 etal shut off the backlight but the screen stays active - which is no big deal and a very small power draw. It's the backlight that kills ya.