when it's 'off', when you don't hear anything, you are not allowing power to get to the batteries to charge them, which is why you might hear humming, or a fan, etc.
when you are plugged into power, there's never a reason to turn 'off' your RV, leave it on, electricity never hurt any RV!
the only real reason to turn 'off' the RV, or technically to 'disconnect' the batteries, is when it's in 'storage', or parked somewhere without any power, when you are not camping or otherwise using it. This keeps small phantom draws from drawing down the batteries.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
110,000+mi since '14 - US, Alaska, Canada (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )b