One basic thing is that all electtic motors operate better with the proper voltage.
Being plugged into shore power, or having the engine running provides a higher voltage to run the motors.
The other side of the coin is safety, that is why the Parking brake must be set, and the key is in the ignition, mine must be in the run position, but the engine can be on or off.
If your batteries are in good shape, or you just finished driving, you should be fine with engine off and no shore power. I usually connect to shore power when posible to level and open slides.
Our Phaetons should be level before operating the slides.
Against popular opinions, I commonly put my rear slides 1/2way out for loading at home, to get access to the rear. Then put them back in.....always hold your button depressed for 3 or 4 sec after the slide has stopped. And I do this on the street. Would not do this with the big slides however.
2014 40QBH Phaeton DP Cummins 380HP ISL, Freightliner XC, 2014 Jeep Trailhawk TOAD
Blue Ox Aventa tow bar, SMI Air Force One -South Orange County Ca.