James, the Coach Power switch at the entry was meant for dealers to use for displaying coaches on their lots, thus the moniker "salesman's switch". New owners usually interpret it as a way to conserve battery power, and to an extent that is correct. There's a but...
But the switch wasn't designed to be constantly used, esp. by owners, and it can wear and fail. Besides, it only cuts off some interior circuits. Many wonder how their batteries ended up dead when they shut off the Coach Power switch. To properly store the rig you must turn off the large main battery switches, usually seen near the battery tray/200amp fuse area. Even then the engine, if electronic, can scavenge some mAh while just parked - it's ECM is just snoozing. So if not plugged in or solar panel exposed, the batteries may deplete in time.
As our here much-missed and dear friend, Ken, used to tell us after replacing it and it's latching solenoid, "Leave the d@&!#* salesman's switch alone!"
Joel