Ours send even when unit is asleep...basically only the power to the handheld unit is asleep...the black box is always on...one of the causes why our batteries die when OOS for an extended time....right now I have the main power disconnected...no location since I unplugged it.
I used to leave it plugged in but after the 10 days or so of not moving I'd have to boost myself...
No it only does that for I think 24 hours. I will verify time frame tomorrow but it does not go forever.