I ended up talking to them and they said to expect them to stay on for about 75 minutes until the BCM turns off power to the 12V jack in the console that they are pulling the sense wire off of.
Anybody that's installed the MB Quart system, do the blue LEDs on your amp stay on all the time when parked? I just installed mine today and they are still on an hour and a half after I got home.
At the off-rodeo, the instructor recommended using the top of the front bumper as a good guide for fording depth. Obviously not the easiest to translate to backing in on an angled ramp, but should at least give you a starting point.