What kind of coach do you have? My previous Monaco did NOT charge the chassis batteries when connected to shore power, so the chassis batteries were usually dead after a month or so -- until I installed this
-- on that coach, we left it connected, fridge on, water heater ready to go, a/c on to keep things from melting, 24/7/365. Not fun on the electric bill - but gave me peace of mind and it was ready to go at a moment's notice, which is primarily how we travel (I hate planning!)
Our Newmar charges both chassis and house batteries via a BIRD, so we leave that connected as well.